The Red Sox traded with the San Diego Padres for first baseman Gonzalez in the off-season with the intention of signing the left-handed hitter to a long-term contract.
The contract represents the ninth biggest aggregate sum ever agreed to in the major leagues and second-largest for the Red Sox behind an eight-year, $160 million deal given to Manny Ramirez before the 2001 season.
Gonzalez, a three-time All-Star and twice Gold Glove winner, is hitting .268 with one home run and seven runs batted in this season as Boston has gotten off to a 2-9 start.
The 28-year-old Gonzalez, who broke into the majors with the Texas Rangers in 2004, has a career batting average of .284 with 169 homers and 532 RBIs.
(Writing by Larry Fine in New York, Editing by Justin Palmer)