Hooper was born on August 24, 1887, in Bell Station, California. His family had migrated to California as many other families from the United States due to the California Gold Rush. His father, Joseph "Joe" Hooper, was born in Morrell, Prince Edward Island in Canada. Joe was the fourth child and second boy born to English-born William Hooper, Harry's grandfather, and his Portuguese wife Louisa.

Breaking into the majors with the Red Sox in 1909, Hooper played in 81 games and hit .282. Between 1910 and 1915, he teamed with Tris Speaker (CF) and Duffy Lewis (LF) to form the Golden Outfield, one of the finest outfield trios in baseball history. Religious differences may have been the biggest challenge for the Golden Outfield. At the time, a common Protestant sentiment was that Catholics would move to their communities and change the established culture. Speaker, who was a Protestant, once went a year without speaking to Hooper or Lewis, who were both Catholic.  Though Hooper was a hard competitor on the field, he became known for his likable personality and sense of humor, which contrasted with Speaker's tough exterior. Hooper became a favorite with the fans and he established a reputation as a clutch player. He became known as a top-caliber defensive right fielder and a solid leadoff hitter. He invented a maneuver known as the "rump-slide" for catching shallow fly balls.  In 1910 Hooper played 155 games and hit .267 in a league-leading 688 plate appearances, marking the first of eleven consecutive seasons where he had at least 564 plate appearances. He led all AL outfielders with 30 assists that season, but he also committed a league-high 18 errors. In 130 games the next year, Hooper hit .311; the outfield trio of Hooper, Lewis and Speaker hit .315 combined.  Hooper's batting average dropped to .242 in 1912. Boston won the 1912 World Series, during which Hooper made a catch that The Pittsburgh Press referred to as one of the finest plays in baseball history. The paper noted that Hooper "does not seek the limelight. He is reserved and bashful, and every action of his upon the baseball field plainly shows these qualities." On May 30, 1913, Hooper became the first player to hit a home run to lead off both games of a doubleheader, a mark only matched by Rickey Henderson and Brady Anderson over 80 years later. In 1914, he recorded 230 putouts in right field, which was the first of several seasons in which he finished in the top three in that category among right fielders.  On October 13, 1915, in game five of the 1915 World Series, he became the second player to hit two home runs in a single World Series game. Duffy contributed a third home run as the Red Sox won another world championship four games to one. Hooper was also the captain of the Red Sox in 1919. Hooper became known for talking Boston manager Ed Barrow into converting Babe Ruth from a pitcher to an outfielder.

what did Hooper do for Red Sox?
Between 1910 and 1915, he teamed with Tris Speaker (CF) and Duffy Lewis (LF) to form the Golden Outfield, one of the finest outfield trios in baseball history.