Company lists · Data refreshed September 2026
Top 9 Investigative agencies based in Houston, United States
RevenueBase identified 28 investigative agencies headquartered in Houston, United States as of September 2026 and tracks 402 professional contacts across them, including 105 with verified work emails. New York is the largest hub.
This list covers investigative agencies headquartered in Houston, United States, 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 20, 2026.
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.
The 9 largest investigative agencies based in Houston, United States
Ranked by team size| # | Company | Contacts | |||
|---|---|---|---|---|---|
| 1 | 16 contacts → | ||||
Indirect evidence “PPI Security is a company based out of HOUSTON, TEXAS, United States.” Source: RevenueBase Database · checked Sep 20, 2026Thanks. The Data Team will review it. | |||||
| 2 | 11 contacts → | ||||
Strong evidence “Gradoni & Associates offers a wide range of investigative services such as Criminal Defense Investigations, Surveillance, Background Investigations, etc.” Source: RevenueBase Database · checked Sep 20, 2026Thanks. The Data Team will review it. | |||||
| 3 | 9 contacts → | ||||
Strong evidence “Swailes & Company is a licensed investigative and security consulting company headquartered in Houston, Texas.” Source: RevenueBase Database · checked Sep 20, 2026Thanks. The Data Team will review it. | |||||
| 4 | 7 contacts → | ||||
Strong evidence “Delta Intel Group is a premium full-service Private Investigation Firm based in Houston, Texas.” Source: RevenueBase Database · checked Sep 20, 2026Thanks. The Data Team will review it. | |||||
| 5 | 6 contacts → | ||||
Strong evidence “Private Investigations Agency Our Purpose To Establish Clarity in Matters of Fraud, Deception or that which is Hidden 713 807-8811 bpellerin@texasinvestigators.com Licensed…” Source: RevenueBase Database · checked Sep 20, 2026Thanks. The Data Team will review it. | |||||
| 6 | 5 contacts → | ||||
Indirect evidence Source: RevenueBase Database · checked Sep 20, 2026Thanks. The Data Team will review it. | |||||
| 7 | 3 contacts → | ||||
Strong evidence “Frizell Group International, LLC ("Frizell Group"), is a corporate investigations and risk advisory firm specializing in high-stakes matters involving fraud, employee misconduct…” Source: RevenueBase Database · checked Sep 20, 2026Thanks. The Data Team will review it. | |||||
| 8 | 2 contacts → | ||||
Strong evidence “At Main Security and Investigations, our simple philosophy is to deliver professional, integrated security solutions and private investigative services for a wide range of clients…” Source: RevenueBase Database · checked Sep 20, 2026Thanks. The Data Team will review it. | |||||
| 9 | 1 contacts → | ||||
Strong evidence “The President and Owner of Wilson Investigations LLC is Timothy D.” Source: RevenueBase Database · checked Sep 20, 2026Thanks. The Data Team will review it. | |||||
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: investigative agencies. 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 investigative agencies.
- Partial evidence
- Its own public description names part of investigative agencies, so it works in or next to the category without describing itself that way.
- Indirect evidence
- The description shown does not name investigative agencies. 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 9 of 28 investigative agencies based in Houston, United States
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Investigative agencies based in Houston, United States at a glance
As of Sep 20, 2026Companies by employee count
Email recency for this list is measured across the whole United States list rather than for Houston, so it is reported there. Company counts and contact totals on this page are exact for Houston, over 28 companies.
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 investigative agencies, 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.
- What qualifies
- Companies headquartered in Houston, United States whose own description of what they do matches “investigative agencies”. 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 investigative agencies), 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 investigative agencies, and records with no verified work email. Companies headquartered outside Houston are excluded even when they keep an office there.
- 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, 105 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 20, 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.
Investigative agencies by metro in the United States
- Investigative agencies in New York53
- Investigative agencies in Washington43
- Investigative agencies in Houston28
- Investigative agencies in Los Angeles25
- Investigative agencies in Miami25
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 investigative agencies, 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 investigative agencies are there based in Houston, United States?
RevenueBase identified 28 investigative agencies headquartered in Houston, United States 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?
PPI Security, headquartered in Houston, tops this list with the largest team on record.
Which city has the most investigative agencies?
New York leads with 53 headquartered companies, followed by Washington (43) and Houston (28).
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 105 verified decision-maker contacts tracked across these 28 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 20, 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.
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