New York & Long Island

Private Investigation and Security Consulting

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call us at 1-888-698-0077
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Radius Investigations

Radius Investigations is an investigation and security consulting agency based in New York. We are dedicated to providing our clients with the highest quality of investigation services, including surveillance, due diligence, business intelligence, and security consulting services. We serve a wide range of clients, including individual private clients, law firms of every size and specialty, multi-national corporations, hedge funds, financiers, and religious institutions.


We provide the following investigative services:

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Computer forensics



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background checks


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Security Services

Security Services

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Radius Investigations has associate investigators and confidential sources throughout all of North America, Europe, Latin America, Africa, the Asia Pacific Region, and the Middle East.

Clients of Radius Investigations receive a user name to log in to a secure portal in order to see how their cases are progressing. The online portal also provides our clients with the ability to watch evidentiary videos, see new updates, and monitor the status of their case through our fully-encrypted and secured website.

Our experienced team of professionals are licensed, bonded, and insured to conduct surveillance and all other forms of investigations in New York, across the United States, and Globally. Our primary office is located on Rt. 110, Melville, in Suffolk County, Long Island, with easy access to Long Island, Manhattan, Queens, Brooklyn, the Bronx, Staten Island, and Westchester.

In addition, Radius Investigations maintains an extensive network of investigators, contacts, and sources throughout the world, ensuring that we can provide responsive, timely, and accurate investigations anywhere our clients’ needs may take us.

Our investigators are dedicated to keeping clients informed throughout the entire investigative process. We believe that by maintaining communication, we can better assist clients and provide peace of mind during otherwise stressful situations. Radius Investigations offers clients discipline, quick-thinking, and a strong work ethic dedicated to preserving our clients’ privacy and confidentiality while pursuing the objective facts with the utmost integrity.

Litigation Support

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Employee Background

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Child Custody

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Client testimonials


David Esposito

"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."

Entrepreneur, Business Professional - Wiki Travel

Cris Armenta

"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."

M. Cris Armenta - The Armenta Law Firm

Richard E. Duggan, AHFI

"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."

Fraud Investigator at Verisys Investigations Inc. - Media Wiki

Lisa Martelloni

"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."

Product Management Engineering - Max Mobilcom

Stephen Federlein

"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."

Infrastructure Specialist at Festo - Doom Inc.

Larry Boritz

"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."

New York State Regional Director at United Studios Of Self Defense

Lory Metka

"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."

March 19, 2014

Rita Y.

"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!"

May 31, 2013

Sheila L.

"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."

March 28, 2014

Gary R.

"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."

October 14, 2015

Joseph R.

"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!"

October 15, 2015

Hasan S.

"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!"

October 14, 2015

David E.

"The guys are the best!
Real pros who never give up - and they always find their man! I have used Radius for several different projects and always find them to be professional, thorough and diligent - you will not be disappointed using them."

October 14, 2015