NCIS Technical Investigators are responsible for conducting the Navy's Technical Surveillance Countermeasures mission.  They conduct investigations to protect the Department of the Navy's classified information and critical infrastructure from being compromised by technical means (for example, through covert listening devices or other surveillance technology) employed by foreign intelligence or other parties. These NCIS professionals assess vulnerabilities and identify and resolve technical surveillance threats.

NCIS Technical Investigators serve in TSCM units at NCIS Headquarters and select NCIS field offices around the world, where they are best positioned to meet the needs of the U.S. Navy commands they support.

In addition to conducting technical surveillance countermeasures investigations for the Navy, NCIS is the Department of the Navy's program manager for TSCM, working in concert with the U.S. Marine Corps' TSCM program and other DoD TSCM programs to provide policy guidance and other support.