The younger brother of Georgetown Hall of Famer Jack Flavin, Don Flavin followed his brother's path from Portland, ME to the Hilltop in 1924, where he played three seasons on the football team and two on the basketball team. A reserve forward in 1926, he earned a starting role in 1926-27, finishing fourth in scoring during an abbreviated nine game season.

Following Georgetown, Flavin moved to New York, where he became vice president of the Charles Francis Press, a prominent New York printer located across from Pennsylvania Station on 8th Ave. His son Don Jr. (C'61) was a four year member of the Georgetown sailing team and its captain in 1960.