From Montauk to Coney Island
We Are Long Island’s Private Eyes

Available 24/7 1-888-698-0077

Radius Investigations’ Private Investigators serve

the Long Island and New York City communities.

Radius Investigations – Your Long Island Private Investigators

We are Radius Investigations Inc., born and raised on Long Island, New York, and located near the center of the island in Hauppauge to stay close to our roots. Our licensed and bonded agency of private investigators are committed to providing quality and transparent private investigation and security services to Nassau County, Suffolk County, and New York City. Our clientele are as diverse as the Long Island community, including law firms, small-to-medium sized businesses, local and multi-national corporations, private clients, high-profile clients, financial professionals, religious institutions, and non-profits.

Why Choose Us?

Simple. We Are “No Bull”:

We are here to find answers, not take you for a ride.

We set ourselves apart from the rest with these simple rules:



From the moment we make contact, we provide top-quality services from bonded and licensed private investigators that deal in facts. We offer advice and solutions that will achieve the results you need for your case, not just sell you unnecessary fluff. Our final reports are comprehensive, thorough, and get straight to the point.


We don’t run and hide. We work with you every step of the way in getting intelligence. All of our clients have access to our online portal where you can view any recent updates to your case, as well as any video or photo documentation. We are available 24/7 to assist you and answer questions to your case.



As a veteran owned agency, we take on the military philosophy of never giving up and working as a team. We will work tirelessly and access our vast amount of resources and networks to give you the information you need to make informed decisions on your situation.


From our national and local charity work to you, our compassion towards your search for answers will never leave you feeling like nothing more than a number or case file. When you speak with us, we listen intently to understand your situation and give the best advice and strategies for your case, not just wait for you to stop talking so we can make our point.

What Our Clients Say About Us:

“Mr. Seifer provides a very professional, trustworthy service and is very knowledgeable in his field. He goes above and beyond to accommodate his clients to get the best results.”

-Lisa Martelloni

Product Management Engineering – Max Mobilcom
lisa testimonial long island private investigator

"Radius Investigations went the extra, extra mile for me trying to locate the executor and beneficiary of my fathers estate. Heart broken, I was pretty down after a month of searching and effort but he answered my prayers and found my brothers son and my brother ONLY BECAUSE he went the extra mile for me. As a life long Deep Sea - Merchant Mariner and seven year Veteran active service of the USCG and USN and 17 years USNR - this is not BS. I do not BS. I totally endorse Radius Investigations. Thank You Mathew."

-Bob Kuskis

First Officer – U.S. Navy Military Sealift Command

“I will start with a conclusion – the job was done successfully! I have never dealt with private investigators, and i am glad i met a professional with a caliber of a person like Matthew – easy to deal with, comforting, professional, provided real solution and alternatives. My case was related to the divorce and all the investigation was legit and useful. Prompt, trustworthy, responsive, and importantly reliable. Thank you for your help!”

-Hasan S.

“I’m someone that was been involved with Law Enforcement for over 25 years including a career with the NYPD as a front line supervisor as a Sergeant in the NYPD. I can tell you from firsthand experience, both personal and professional dealings with Mr. Seifer, he is a true professional in his field, however he has a great asset that is truly lacking out there lately, that is… “Honesty & Integrity”. If he promises you something he delivers! He is always prompt, courteous, and highly competent to handle any task he’s given. He can be trusted with the most sensitive of issues to the most routine.”

-Larry Boritz

New York State Regional Director at United Studios Of Self Defense

“I spoke with Matt the week after Thanksgiving about locating my car. While he wasn’t able to help, he was a kind voice of direction in a sea of rude and unhelpful local police officers. Months later he followed up with me to find out if the vehicle was ever located. Thankfully it was. I am thankful for the kindness and compassion showed.”

-Sheila L.

“I have retained Radius Investigations to perform various investigative work. They always go above and beyond. I would recommend Radius to anyone or any entity that requires the assistance of a private investigator.”

-Gary R.

"From my first contact with the people at Radius, they were extremely respectful and professional. They were able to explain to me exactly what they were going to do to help me and told me how much it would cost. Even better, they stayed under my budget and finished sooner than I had expected. I have spoken with many investigative firms in the past and will continue to go back to Radius if I need investigative services again. They were excellent in every way."

-Aviva M.


"I knew going in that the answers I was looking for would be close to impossible to get without going through the court system. Erin was not only very professional, but also very emphatic and talked to me as a friend and not just a client whose money she wanted. I hired another PI before RI, and they didn’t even put 1/8 of an effort as Erin did to help me. I was kept in the loop throughout the process and never felt like my case was being ignored. I would highly recommend working with Radius Investigation for your next project especially if you’re working with Erin."

-John S.


“Even though I am experienced investigator, I rely on Radius for anything that happens in NY. They have quickly and more important, accurately supported my cases when it moved into the NY area or I needed a knowledgeable local investigator to gather documents”

-Gordon Adkins

Private Investigator


"Outstanding investigative services, communication and resources! Great working knowledge and skill sets!"

-John Temblador



“Matt is one of the best PI’s I have worked with. I get excellent results from his investigations that I have used to obtain a fair and reasonable settlement. He is very creative when it comes getting information on a subject. I highly recommend his services.”

-Lory Metka

“Matt was the first to answer my request in finding “my sister”. He told me I had the “key ingredients” (a lot of information) for a search, and that he would refer me to someone in Pennsylvania as his business is in New York. He made a contact while I was on the phone with him and asked the PI in PA to give me a call and the reason why he should contact me. I very much appreciated his time and his concern. I believe our conversation covered all the pertinent details in about ten minutes. Thanks, Matt!”

-Rita Y.

“These guys are amazing. Quality professional service at an affordable price. As an attorney, time and time again I’ve turned to Radius in desperate situations where I needed a quality investigator to immediately help me locate someone, or get papers served in a timely and no nonsense manner, and they have never let me down. I highly recommend them to anyone who needs an investigator they can trust to get the job done!”

-Joseph R.

“I hired Matt Seifer several times and all times he produced results in a timely manner and the results were extremely thorough and detailed. My Privacy was kept just that, private. I would highly recommend Matt Seifer for your business, legal and personal matters. I can be contacted for further details.”

-David Esposito

Entrepreneur, Business Professional – Wiki Travel

david esposito nyc private investigations

“Radius Investigations has provided service to me and my clients nationwide for several years, with impeccable and responsive service and excellent contacts and field work. I have been impressed with the nationwide contacts and level of service and recommend them highly. They are my go‐to investigators.”

-Cris Armenta

The Armenta Law Firm

“I have worked for, and alongside Matthew Seifer for seven years and know him to be an intrepid investigator, who is thorough and professional. He has a broad range of experience and solid technical skills. Matt is ethical, conscientious and responsible in all matters of security matters and investigations.”

-Richard E. Duggan

AHFI Fraud Investigator at Verisys Investigations Inc. – Media Wiki

richard duggan new york private investigators

“As the owner of a security business installing surveillance and burglar alarm systems I had the pleasure of meeting Matthew. I can honestly tell you that over the past 7 years I have known him that he is a man that stands behind is word and is a true professional at what he does.”

-Stephen Federlein

Infrastructure Specialist at Festo – Doom Inc.

stephen long island private investigations

Our Lead Investigator

Meet Matthew Seifer: Expert Licensed Private Investigator, Registered Armed Guard, Technical Surveillance Countermeasure (TSCM) Specialist, and NYS DCJS Certified Instructor

Matthew Seifer Long Island Private InvestigatorMatthew Seifer formed Radius Investigations in 2007. He is a self-employed business owner, retired from the U.S. Army, and has over 26 years in the private sector. Matthew has established a national and international network of licensed professionals that are from law enforcement, private investigation, government, insurance industry, civil and criminal legal community, community activists, small business owners, and clients. With his expertise and network, he can ensure that your needs will be answered anywhere in the world at anytime.

Seifer has been described as dedicated, compassionate, receptive, trustworthy, and diligent with his clients and community. He oversees every case and will follow through until the client has the answers they need to make an educated and informed decision.

 Our expertise is unmatched. Here are a few of our many specialty services:

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Please note that all of our training programs, including active shooter seminars and drills, anti-crime seminars, security guard training, and private investigator courses, have moved to our new training division, Guardian Security Training. Please visit their website for more information and the latest class schedule.

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Long Island: 

150 Motor Parkway, Suite LL20

Hauppauge, NY 11788


Long Island: 

150 Motor Parkway, Suite LL20

Hauppauge, NY 11788






 New York City:

1177 Avenue of the Americas, 5th Floor

New York, NY 10036


 New York City:

1177 Avenue of the Americas, 5th Floor

New York, NY 10036