The Chicago Tribune said the 74-year-old former Northwestern University professor died of cancer at his home in Santa Monica, Calif.
"He truly had an impact on the military," Army Gen. Wesley Clark said in a written statement. "He gave many of us the reassurance that someone out there knew us, cared about us and could help see our best interests as a nation and a military were looked after."
Moskos was an Army veteran who spent much of his career observing military life and the interaction of the armed forces and the civilian world. His research included racial integration in the ranks and what motivated people to join the service.
In 1993, Moskos was an adviser to the Joint Chiefs of Staff on the controversial policy toward homosexuals in the military. Colleagues said Moskos' goal was to find an area of common agreement on the matter.
Funeral services will be held Friday in Chicago.