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100% Confidential Consultation

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Radius Investigations – The Expert Private Investigators

Radius Investigations Inc. is a private investigation, security consulting, and training agency based on Long Island in New York, near the Metro New York City area. We are dedicated to providing our clients with the highest quality of investigation services, including surveillance, due diligence, business intelligence, technology forensics, 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.

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


  • Corporate Investigations
  • Matrimonial Investigations
  • Child Custody Investigations
  • Missing Persons Investigations
  • Criminal Investigations and Litigation Support
  • Surveillance and Undercover Investigation
  • Computer, Smartphone, and iPhone Forensics
  • Social Media Investigations
  • Bug Sweeping (TSCM)
  • Data Retrieval and Acquisition
  • Digital Evidence and e-Discovery
  • Cyberbullying / Harassment Investigation
  • Personal Background Checks
  • Employee Background Checks
  • Business Intelligence
  • International Investigations
  • Nanny Background Checks
  • Caregiver Background Checks
  • Tenant Background Checks
  • Security Threat Assessments
  • Private Security Services
  • Surveillance
  • Aerial Drone Surveillance
  • Stalking and Harassment Investigation
  • Threat Investigation
  • Careers at Radius Investigations
  • Private Investigator Introductory Course
  • NYS Private Investigator License Exam Prep
  • Security Guard Training
  • Anti-Crime Technique Seminars

Our expertise is unmatched.

Tap the Icons to See What We Do:


  • Corporate Investigations
  • Security and Threat Assessments
  • Employment Investigations
  • Computer Forensics and
    Cell Phone Analysis
  • Matrimonial Investigations
  • Child Custody Investigations
  • Missing Person Investigations
  • Criminal Investigations and Litigation Support
  • Surveillance and Undercover Investigation

Careers and Training

  • Careers at Radius Investigations
  • NYS Certified Security Guard Training
  • Private Investigator Introductory Course
  • NYS Private Investigator License Exam Prep

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 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 “No Bull” Promise:

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

Click below to learn how 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 about 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.

Who We Are

Radius Investigations has a network of associate investigators and confidential sources throughout all of North America, Europe, Latin America, Africa, the Asia Pacific Region, and the Middle East. This ensures that we can provide responsive, timely, and accurate investigations anywhere our clients’ needs may take us.

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 Motor Parkway, Hauppauge, in Suffolk County, Long Island, NY, with easy access to Long Island, New York City, Manhattan, Queens, Brooklyn, the Bronx, Staten Island, New Jersey, and Westchester.

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, receive updates, and monitor the status of their case through our fully-encrypted and secured website.

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 clients’ privacy and confidentiality, while pursuing the objective facts with the utmost integrity.

Client testimonials

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“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 May 13, 2017

Radius Investigations Long Island Private Investigator Services - Blog Directory

Long Island: 

Radius Investigations Inc

150 Motor Parkway, Suite LL20

Hauppauge, NY 11788


 New York City:

The Americas Towers

1177 Avenue of the Americas, 5th Floor

New York, NY 10036