The Red Sox trailed 2-1 in the seventh inning when Jonny Gomes led off with a double against Tigers starter Max Scherzer (0-1). After Stephen Drew struck out, Xander Bogaerts drew a walk, chasing Scherzer.
The Tigers brought in Jose Veras, Victorino greeted him by socking a pitch off the top of Fenway Park's "Green Monster" left-field wall for a grand slam, and the Red Sox held on to win their third AL pennant in 10 years.
They advance to the 2013 World Series, where they will host the National League champion St. Louis Cardinals Wednesday in Game 1.
Victor Martinez drove in a pair of runs for the Tigers, whose bullpen allowed seven runs, six hits and two grand slams in the two ALCS games started by Scherzer.