The Giants reached the playoffs as winners of the NL West. In Game 4 of the NL Division Series (NLDS) against the Atlanta Braves, with San Francisco leading 3–2, Casilla pitched a scoreless seventh inning. He also got two outs in the eighth inning before left-hander Javier López was summoned to finish the inning. The Giants won 3–2, clinching a trip to the NL Championship Series (NLCS) against the Philadelphia Phillies. Casilla came on in relief in Game 2 with the Giants trailing 3–1, the bases loaded, but two outs in the seventh. However, he gave up a bases-clearing double to Jimmy Rollins, and San Francisco lost 6–1. In Game 4, he allowed another bases-clearing double, this time to Placido Polanco but with only two men on base. Casilla also gave up a run of his own on a wild pitch. However, the Giants won 6–5 and went on to defeat the Phillies in six games. Against the Texas Rangers in Game 1 of the World Series, Casilla entered with the Giants up 8–4 and two runners on in the sixth. He struck out Elvis Andrus, then pitched a scoreless seventh as the Giants won 11–7. Casilla earned his first World Series ring as the Giants won the series in five games to win their first title since 1954.