Delahanty was one of five brothers to become Major League Baseball players, including older brother Ed Delahanty. He played his first full season in 1904, in which he batted .285 with the Beaneaters. He was traded mid-season by the Senators to the Tigers in 1909 for Germany Schaefer and played in his only World Series that season, batting .346 with 4 RBI in 7 games against the Pittsburgh Pirates. He finished his playing career in the Federal League. In 1,186 career games, Delahanty had 1,159 hits with 19 home runs and 151 stolen bases.
In 1905, a couple of home runs really traveled. Jim Delehanty, brother of Hall of Famer Ed Delehanty, hit a homer that left the park in Boston and bounced onto a slow-moving freight train. When the ball was retrieved, the train was in Connecticut. The next batter drilled another out of the stadium and into a passing car. Altogether, the two shots went 106 miles.