The school did not release details of Millikan's death in a release Thursday.
He coached the Terrapins from 1950-1967, compiling an overall 243-182 record.
Maryland reached the NCAA Tournament's Elite Eight and won the Atlantic Coast Conference title in the 1957-58 season with a 22-7 mark.
One of his players was current Maryland Coach Gary Williams from 1964-67.
"He was my coach for all four years," Williams said on the school's Web site. "I think his strength was he was a very strict fundamentals coach. That was an important part of a number of us becoming head coaches."
Williams added Millikan's coaching style helped inspire a number of other former players to become successful coaches in their own right, including Colorado's Joe Harrington.