Originally affiliated with the Florida Marlins, the Sea Dogs became part of the Red Sox system for the 2003 season.

City manager Robert Ganley led efforts to renovate Hadlock Field and return professional baseball to Portland.

The team won its first game, defeating the Reading Phillies on the road 2–1, with the help of a 14th-inning home run by future major league catcher Charles Johnson.

[citation needed] The team won its sole league title on September 17, 2006, defeating the Akron Aeros 8–5, in a rematch of the series from the previous year.

[7] Ahead of the 2023 season, the Sea Dogs' longtime owners, the Burke family, sold the team to Diamond Baseball Holdings.

[10] Hadlock Field is often visited by vacationing celebrities, such as former NFL coach Bill Parcells, former U.S. President George H. W. Bush, and his wife Barbara.