Brandon Crawford became the first shortstop in MLB post-season history to hit a grand slam homer, which sent the Giants on their way to winning the wildcard match in Pittsburgh.
Giants starting pitcher Madison Bumgarner pitched the shutout, striking out 10 as he allowed just four hits all night.
Brandon Belt had three RBIs for the winners, while catcher Buster Posey added in another on a perfect night for the 2012 World Series champions.
Edinson Volquez suffered on the mound for the Pirates, his five innings conceding five hits and five runs - four of which were to the Crawford homer.
Game one of the Giants' series with the Nationals is on Friday in Washington.