Company lists · Data refreshed September 2026

Top 25 Inside sales outsourcing firms worldwide

Name: Inside sales outsourcing firms worldwide
Creator: RevenueBase
License: https://creativecommons.org/licenses/by/4.0/

Compiled by the RevenueBase Data Team Data refreshed Sep 28, 2026 13,644 companies tracked

RevenueBase identified 13,644 inside sales outsourcing firms worldwide as of September 2026 and tracks 202,271 professional contacts across them, including 19,580 with verified work emails. The United States is the largest market and London the largest hub.

This list covers inside sales outsourcing firms worldwide, matched on what each company actually does as described in its own words. Ranked by team size, largest first. Every row shows the company's own description, its RevenueBase Smart Search rating, and when it was last checked. Data refreshed September 28, 2026. Country and city lists for inside sales outsourcing firms follow the table.

Published by RevenueBase, a B2B data infrastructure company. This list was built with RevenueBase Smart Search, the natural-language company search RevenueBase customers use to build their own targeted lists and unlock verified emails and direct dials at the companies on them. How these lists are built and judged.

How to read this list HQ checked on every row RevenueBase Smart Search rating on every row Refreshed Sep 28, 2026 86% judged on-target in blind review

13,644Companies

202,271Contacts tracked

19,580Verified emails

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The 25 largest inside sales outsourcing firms worldwide

Ranked by team size

Top 25 of 13,644 inside sales outsourcing firms worldwide, ranked by team size, largest first. Data refreshed Sep 28, 2026. RevenueBase Smart Search rates how each company's information relates to inside sales outsourcing firms: strong evidence (its own description names it), partial (names part of it), indirect (matched on the rest of its profile rather than the description shown). Click a contact count to view that company's people.
#	Company	RevenueBase Smart Search	Headquarters	Employees	Contacts
1	Emtelco S.A	Indirect evidence	Medellín, ColombiaHQ checked Sep 28, 2026	10001+	4,998 contacts →
	Indirect evidence “Maximizamos el valor de cada contacto de las empresas con sus clientes, gestionando los procesos de relacionamiento a través de canales tefónicos, virtuales y presenciales.” Source: RevenueBase Database · checked Sep 28, 2026
2	Liderança Serviços	Indirect evidence	São José, BrazilHQ checked Sep 28, 2026	10001+	4,504 contacts →
	Indirect evidence “Atuamos nos principais setores de terceirização, e somos pioneiros na implantação de contratos à distância.” Source: RevenueBase Database · checked Sep 28, 2026
3	Marketsource INC	Partial evidence	Alpharetta, GA, United StatesHQ checked Sep 28, 2026	5,001-10,000	3,063 contacts →
	Partial evidence “MarketSource, an Allegis Group company, is a sales acceleration company focused on delivering better outcomes for many of the world’s most iconic brands.” Source: RevenueBase Database · checked Sep 28, 2026
4	Advanced Call Center Technologies, LLC	Indirect evidence	Berwyn, PA, United StatesHQ checked Sep 28, 2026	5,001-10,000	2,774 contacts →
	Indirect evidence “Advanced Call Center Technologies, LLC (ACT) is a premier provider of domestic (USA), near shore and far shore outsourced call center services to the financial services, mortgage…” Source: RevenueBase Database · checked Sep 28, 2026
5	Stream Global Services	Partial evidence	Eagan, MN, United StatesHQ checked Sep 28, 2026	10001+	2,772 contacts →
	Partial evidence “Stream Global Services is a premium business process outsource (BPO) service provider specializing in customer relationship management solutions including sales, customer care…” Source: RevenueBase Database · checked Sep 28, 2026
6	Marketstar	Strong evidence	Ogden, UT, United StatesHQ checked Sep 28, 2026	1,001-5,000	2,446 contacts →
	Strong evidence “MarketStar is a global B2B sales outsourcing leader with 38+ years of experience driving predictable revenue growth.” Source: RevenueBase Database · checked Sep 28, 2026
7	Denave	Indirect evidence	Noida, IndiaHQ checked Sep 28, 2026	5,001-10,000	2,270 contacts →
	Indirect evidence “We are revenue AI-X-lerators.” Source: RevenueBase Database · checked Sep 28, 2026
8	Allied Global	Indirect evidence	GuatemalaHQ checked Sep 28, 2026	5,001-10,000	1,979 contacts →
	Indirect evidence “Regardless of your Company’s size (from Start-ups to Fortune 500), business vertical or service requirements, we act as a seamless extension of your team to help you grow, and…” Source: RevenueBase Database · checked Sep 28, 2026
9	Webhelp Enterprise	Partial evidence	Paris, FranceHQ checked Sep 28, 2026	10001+	1,795 contacts →
	Partial evidence “The Concentrix B2B sales practice is here to design, build and run projects for our clients.” Source: RevenueBase Database · checked Sep 28, 2026
10	Full Potential Solutions	Partial evidence	Waltham, MA, United StatesHQ checked Sep 28, 2026	1,001-5,000	1,238 contacts →
	Partial evidence “Full Potential Solutions (FPS) is a new kind of performance-based outsourcing firm that puts culture and employees first, because we believe that happy, fulfilled teams accomplish…” Source: RevenueBase Database · checked Sep 28, 2026
11	Information Evolution, INC	Partial evidence	Austin, TX, United StatesHQ checked Sep 28, 2026	501-1,000	1,238 contacts →
	Partial evidence “We are a boutique outsourcing firm specializing in keeping our customers' databases up-to-date, accurate, and as robust as possible.” Source: RevenueBase Database · checked Sep 28, 2026
12	The Office Gurus	Indirect evidence	St Petersburg, FL, RussiaHQ checked Sep 28, 2026	1,001-5,000	1,198 contacts →
	Indirect evidence “The Office Gurus (TOG) is a global call center and business process outsource provider of customer care, telemarketing, lead generation, appointment setting, order entry, accounts…” Source: RevenueBase Database · checked Sep 28, 2026
13	crystel.co	Partial evidence	Amman, JordanHQ checked Sep 28, 2026	1,001-5,000	1,128 contacts →
	Partial evidence “Crystel emerged as a leading Outsourcing Service Provider (OSP) since its establishment in Jordan in early 2007.” Source: RevenueBase Database · checked Sep 28, 2026
14	Cience	Indirect evidence	Miami, FL, United StatesHQ checked Sep 28, 2026	201-500	1,068 contacts →
	Indirect evidence “CIENCE Technologies, Inc, founded in 2015 and headquartered in Denver, CO, is a pioneering global company in lead generation software and services, committed to transforming the…” Source: RevenueBase Database · checked Sep 28, 2026
15	B2s Business Support Services	Indirect evidence	Gennevilliers Cedex, FranceHQ checked Sep 28, 2026	10001+	978 contacts →
	Indirect evidence “Expert de la relation client depuis 1996, b2s est le N°1 de l’externalisation de votre relation client en qualité délivrée.” Source: RevenueBase Database · checked Sep 28, 2026
16	Transparent BPO	Partial evidence	Rockville, MD, United StatesHQ checked Sep 28, 2026	1,001-5,000	972 contacts →
	Partial evidence “Transparent BPO was founded to provide its clients with superior nearshore contact center services and business process outsourcing at competitive pricing.” Source: RevenueBase Database · checked Sep 28, 2026
17	Inktel Contact Center Solutions	Indirect evidence	Doral, FL, United StatesHQ checked Sep 28, 2026	1,001-5,000	902 contacts →
	Indirect evidence “Our Company Inktel is a leading business process outsourcer that specializes in creating personalized call center solutions which enable our clients to increase market share…” Source: RevenueBase Database · checked Sep 28, 2026
18	Answernet	Indirect evidence	Horsham, PA, United StatesHQ checked Sep 28, 2026	501-1,000	883 contacts →
	Indirect evidence “If you are interested in growing your business or increasing efficiency, AnswerNet has the expertise, technology, and people to help you take your company to new heights!” Source: RevenueBase Database · checked Sep 28, 2026
19	Servestsa	Indirect evidence	Caracas, VenezuelaHQ checked Sep 28, 2026	n/a	865 contacts →
	Indirect evidence “Statistics first” Source: RevenueBase Database · checked Sep 28, 2026
20	Horatio	Partial evidence	New York, United StatesHQ checked Sep 28, 2026	1,001-5,000	860 contacts →
	Partial evidence “Horatio is a premier, tech-enabled outsourcing partner helping ambitious companies scale customer experience and complex business operations without compromising quality…” Source: RevenueBase Database · checked Sep 28, 2026
21	Memoryblue	Indirect evidence	Tysons, VA, United StatesHQ checked Sep 28, 2026	501-1,000	825 contacts →
	Indirect evidence “memoryBlue is the go-to partner for revenue leaders in B2B Tech looking to grow their pipeline engine.” Source: RevenueBase Database · checked Sep 28, 2026
22	ZAZ Vendas	Indirect evidence	Campinas, BrazilHQ checked Sep 28, 2026	501-1,000	796 contacts →
	Indirect evidence “Em um mercado cada vez mais competitivo, onde a eficiência em vendas massificadas e externas é um desafio constante, a ZAZ Vendas surge como a resposta definitiva.” Source: RevenueBase Database · checked Sep 28, 2026
23	CPM International	Strong evidence	Thame, United KingdomHQ checked Sep 28, 2026	10001+	777 contacts →
	Strong evidence “CPM is an international sales outsourcing and customer experience agency.” Source: RevenueBase Database · checked Sep 28, 2026
24	Sequential Technology International	Indirect evidence	Bethlehem, United StatesHQ checked Sep 28, 2026	1,001-5,000	758 contacts →
	Indirect evidence “Sequential Tech is the trusted outsource partner of wireline/wireless telecommunication, broadband, cable/MSO, and satellite service providers.” Source: RevenueBase Database · checked Sep 28, 2026
25	Abstrakt Marketing Group	Indirect evidence	St Louis, MO, United StatesHQ checked Sep 28, 2026	501-1,000	724 contacts →
	Indirect evidence “We book the qualified meetings that fill your pipeline for any B2B company ready to grow.” Source: RevenueBase Database · checked Sep 28, 2026

RevenueBase Smart Search

RevenueBase Smart Search assesses information from a company’s LinkedIn profile, information supplied directly by the company, its website, and other publicly available sources. It uses that information to rate how closely the company relates to this list’s category: inside sales outsourcing firms. Every row carries its rating and the description the rating was read from, so each one can be checked rather than taken on trust.

Strong evidence: The company's own public description of its business names inside sales outsourcing firms.
Partial evidence: Its own public description names part of inside sales outsourcing firms, so it works in or next to the category without describing itself that way.
Indirect evidence: The description shown does not name inside sales outsourcing firms. The match rests on the rest of the company's public profile rather than the one sentence quoted here, so this is the rating to check first.

RevenueBase Smart Search is how these lists are built: RevenueBase's data engine and AI assemble the companies that match a category defined in a user's own words, so a list can be about what companies actually do rather than about whichever industry code they were filed under.

Showing 25 of 13,644 inside sales outsourcing firms worldwide

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Inside sales outsourcing firms worldwide at a glance

As of Sep 28, 2026

9.7%Verified-email coverage

14.8Average contacts per company

11-50Median size (employees)

2.1%Largest-city concentration · London

Sep 28, 2026Page data refreshed

Companies by employee count

1-10

6,595

11-50

4,332

51-200

1,842

201-500

533

501-1,000

181

1,001-5,000

5,001-10,000

10001+

Email recency is reported on each country list linked below.

How this list was built

Company categories are rarely black and white. RevenueBase reads each company's own description of its business to decide whether it belongs among inside sales outsourcing firms, so some rows will be adjacent to the category rather than pure plays. The description and RevenueBase Smart Search rating on every row are there so you can check each match yourself.

Source: The RevenueBase company graph: 60 million companies and 398.9 million professional contacts resolved from primary sources, queried with RevenueBase Smart Search, the natural-language company search available to every RevenueBase user.
Coverage: Every country. Country and city lists for inside sales outsourcing firms are linked below.
What qualifies: Companies worldwide whose own description of what they do matches “inside sales outsourcing firms”. Matching reads each company's description, not its industry code or its name.
RevenueBase Smart Search: RevenueBase Smart Search is how this list is assembled and how each row is rated. RevenueBase's data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to a category defined in a user's own words. Each row is rated strong evidence (its own description names inside sales outsourcing firms), partial evidence (it names part of the category) or indirect evidence (the description shown names none of it and the match rests on the rest of the company's profile). The description supporting each rating is quoted on the row.
What we exclude: Companies whose own description does not clearly place them among inside sales outsourcing firms, and records with no verified work email.
Match quality: In blind human judging of this matching method, 86% of matched companies were on target. Expect roughly 1 in 7 rows to be adjacent to the category rather than a pure play. Every row shows the company's own description and its RevenueBase Smart Search rating so you can judge each match yourself. Read the full methodology: how the lists are built, how the judging worked, and what the figure means.
Ranking: Team size, largest first: companies are ordered by the number of professionals RevenueBase tracks at each one. Employee ranges shown are reported bands, for context.
Verification: Every listed company carries at least one verified work email, 19,580 across the full list. Contacts re-verify on a rolling cadence, and each contact's own verification date is shown inside RevenueBase.
Refresh: This page's figures were pulled from the company graph on September 28, 2026. Lists refresh periodically as the graph is re-checked.
Corrections: Wrong category, wrong headquarters, or a company that has closed? Use “Report an issue” on any row. Reports go to the RevenueBase Data Team and feed back into the company graph.

Inside sales outsourcing firms by location

70 lists · largest first

Every Inside sales outsourcing firms list RevenueBase publishes, by country and city. Counts are matching companies in each list as of its own refresh date.

Countries

Cities

Frequently asked

What is RevenueBase Smart Search?

RevenueBase Smart Search is how RevenueBase decides which companies belong on this list and how strongly each one fits. Its data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to the category the list is about. Each row is rated strong evidence when the company's own description names inside sales outsourcing firms, partial evidence when it names part of the category, and indirect evidence when the description shown names none of it and the match rests on the rest of the company's profile.

How many inside sales outsourcing firms are there worldwide?

RevenueBase identified 13,644 inside sales outsourcing firms worldwide as of September 2026, matched on each company's own description of what it does rather than its industry code.

What is the largest company on this list?

Emtelco S.A, headquartered in Medellin, tops this list with the largest team on record.

Which country has the most inside sales outsourcing firms?

The United States leads with 2,898 companies, followed by India (1,194) and the United Kingdom (868). Every inside sales outsourcing firms list by country and city is linked on this page.

Which city has the most inside sales outsourcing firms?

London leads with 284 headquartered companies, followed by Pune (218) and New York (145).

How do I get contact information for these companies?

A free RevenueBase account lets you run this exact search and work the top results, verified emails and direct dials included. Upgrading unlocks all 19,580 verified decision-maker contacts tracked across these 13,644 companies.

How current is this list?

The list refreshes periodically as the company graph is re-checked. This page's figures were pulled on September 28, 2026.

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About this data

RevenueBase is a B2B data infrastructure company. Its company graph covers 60 million companies and 398.9 million professional contacts, with emails verified on a rolling cadence rather than scraped once and left to decay. These company lists are generated directly from that graph with RevenueBase Smart Search, the same natural-language company search every RevenueBase user has: describe a market in plain words, get the companies that match, and add verified emails and direct dials for the people at them. It is the same data that powers RevenueBase's B2B data products, and a free account includes 500 credits to start. How these lists are built and judged.