Harry Hooper was born on August 24, 1887 in Bell Station, California. His family had previously 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. Harry was the youngest child in his family of four, having an older sister named Lulu and older twin brothers named George and Charlie. Hooper's mother, Mary Katherine (Keller), was from Frankfurt, Germany.
Hooper was known as a top-caliber defensive right fielder and a solid leadoff hitter. Between 1910 and 1915, he teamed with Tris Speaker (CF) and Duffy Lewis (LF) to form one of the finest outfield trios in baseball history. 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. Beside this, Hooper is only one of two players (Heinie Wagner being the other) to be a part of four Red Sox World Series championships: in 1912, 1915, 1916 and 1918. On October 13, 1915, he became the second player to hit two home runs in a single World Series game. The feat was first accomplished by Patsy Dougherty in game two of the first modern World Series, in 1903. Hooper was also the captain of the Red Sox in 1919.