Marshall Investigative Group
“From insurance fraud, to workers comp claims, Marshall Investigative Group goes the extra mile to find out critical information about a case.”
Best Private Investigators near Oak Park, IL
These agencies serve Oak Park from nearby bases in towns including Chicago, Park Ridge and River Forest.
15 agencies listed · 7 open 24/7 · 10 open weekends · 13 rated 4.5+ · 6 show a license
Data verified October 21, 2026
Chicago Loss Prevention Group
Northshore Process Service Network
“These are the best process servers in Chicago who deliver consistent results day or night.”
RA Private Investigation & Security
“Jordan was very professional, prompt, and courteous when providing his services.”
Usia Private Security
“Chris, and his leadership team, take the time to fully understand our specific needs and tailor their approach to ensure everything runs smoothly”
Confidential Protective Services
“Would definitely Hire him again Thank you !!!!”
The 15 agencies on this page are the private investigators listed for Oak Park, IL. What each one states about its license, its specialties and the areas it covers comes from its own website; ratings and quotes come from public reviews.
Area overview: Oak Park, IL
The 15 agencies on this page are rated from 3.3 to 5.0 across 312 reviews; 1 has 50 or more reviews and 13 are rated 4.5 or higher. 7 are open around the clock; 10 are open on Saturdays and 8 on Sundays. 6 show a license on their websites and 1 has a BBB rating of A or A+. 10 have ten or more years of experience, the longest 34 years. 7 offer urgent consultations and 5 offer a free initial consultation. We have a website on file for all 15 of the agencies on this page; 14 publish a contact page; 12 list a public email and 1 takes bookings online. We count these figures across the agencies on this page; hours and prices change, so confirm the details with the agency before you book.
Which investigators listed for Oak Park describe their work online?
All 15 agencies on this page have a website on file. Those pages are where an agency states its license, the kinds of investigation it takes on, and whether it works mainly for attorneys, for companies or for private clients. That last point changes how a report gets written.
PCI Investigations
“I would recommend it to anyone needing a PI whatever your case may be!”
Chicago Executive Protection - Secure Options Consulting
“Their responsiveness and adaptability have surpassed our expectations, and we wholeheartedly recommend Secure Options Consulting for top-tier security solutions.”
U.S. Security and Protective Services
“Very professional place well structured i recommend them for their services!!!!”
Blue Star Security
“I see Blue Star Security around a lot - always doing the right thing at events to make me feel myself, my family and my employees are safe.”
Citywide Security Group
International Protective Services
Key Chicago Private Investigators
“Jeanne was very thoughtful in her preliminary questioning and then did a great job setting up a strategic plan of action; with excellent follow-through and timely updates.”
Forest Security
“I was on the fence about purchasing a cheaper DIY system but could not be happier going with Forest Security.”
Myers Service
“I spoke to Nerdisa and she was knowledgeable and gracious in answering all of my questions and I had many.”
Why these companies made our list
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