Mike Flanagan's journey in professional baseball began when he was drafted by the Baltimore Orioles in the 15th round of the 1973 MLB Draft. A left-handed pitcher, Flanagan quickly rose through the ranks of the Orioles' minor league system, making his major league debut on September 5, 1975. Over the next decade and a half, he became a fixture in the Orioles' pitching rotation, known for his consistency and skill on the mound.

Flanagan's career reached its peak in 1979 when he won the American League Cy Young Award. That season, he posted a 23-9 record with a 3.08 ERA, leading the league in wins. His performance was instrumental in helping the Orioles capture the American League pennant, although they ultimately fell to the Pittsburgh Pirates in the World Series. Flanagan's ability to control games with his pitching was a key asset for the Orioles during this period.

Throughout the 1980s, Flanagan remained a reliable starter for Baltimore. He was part of the Orioles' 1983 World Series-winning team, contributing to their success with his experience and poise. In the World Series against the Philadelphia Phillies, Flanagan pitched effectively, helping the Orioles secure their championship title.

In 1987, Flanagan was traded to the Toronto Blue Jays, where he continued to perform as a dependable pitcher. During his time with the Blue Jays, he provided veteran leadership and stability to the pitching staff. Flanagan returned to the Orioles in 1991, where he finished his playing career in 1992.

After retiring as a player, Flanagan transitioned into various roles within baseball management and broadcasting. He served as a pitching coach and later as an executive vice president of baseball operations for the Orioles. His deep understanding of the game and his experience as a player allowed him to contribute to the organization in new ways.

Flanagan also worked as a broadcaster, sharing his insights and analysis with fans. His ability to articulate the nuances of pitching and his knowledge of the game made him a respected voice in the baseball community.