International-Directories.com
- International directory of private investigators and related products.
- http://www.ipidirectory.com

PIengine.com
- International directory of investigators, organized geographically.
- http://www.piengine.com/Directory/

The Investigator Directory
- Directory of investigators, process servers, and legal support service providers.
- http://www.investigator-directory.net

Infoguys
- International directory of private investigators.
- http://www.infoguys.com/directory.cfm

PI Resources and Locator
- Directory of private investigators with industry resources.
- http://www.piresourcesandlocator.com/findapi.html

Pimall.com
- Directory of private investigators with resources for this profession.
- http://www.pimall.com/locate/

National Association of Fraud Investigators
- Database of investigators focusing on Fraud Investigation.
- http://www.nafraud.com/

Bail.com
- Directory bail bondsmen, investigators, and defense attorneys, searchable by state.
- http://www.bail.com/

FindPiS.com
- Directory of private investigators searchable by zip code.
- http://www.findpis.com/

ExpertLaw
- Find a private investigator or related service, by specialty and location.
- http://www.expertlaw.com/investigators/

ExpertPages.com
- Investigative service providers, organized by specialty.
- http://expertpages.com/investigate.htm

DetectiveHelp.com
- Searchable database of private investigators in the United States and Canada.
- http://www.detectivehelp.com/

PI Register.Com
- International directory of private investigators.
- http://www.thepiregister.com/

Oklahoma Private Investigators Association
- Offering a statewide directory of investigators.
- http://www.opia.com/

National Association of Investigative Specialists
- Membership directory, searchable by location and specialization.
- http://www.pimall.com/nais/dir.menu.html