Ortiz once again was a major factor in helping lead the Red Sox to their eighth World Series championship. During the regular season, he hit 30 home runs, had 103 RBIs and batted .309. He finished in the top 10 in all 3 categories in the American League.
In the postseason, Ortiz had 5 home runs and 13 RBIs while batting .353. In Game 2 of the American League Division Series against the Tampa Bay Rays, he hit 2 home runs off of Rays' ace pitcher David Price. In Game 2 of the American League Championship Series vs the Detroit Tigers, Ortiz hit a dramatic, game-tying grand slam off of reliever Joaquin Benoit in the bottom of the 8th inning, helping propel the Red Sox to victory. In the World Series against the St. Louis Cardinals, Ortiz hit home runs in both games 1 and 2, had 6 RBIs and batted .688 as the Red Sox won the series 4–2. As a result of his performance, Ortiz was awarded the World Series Most Valuable Player award.
On April 20, before the first game played at Fenway Park since the Boston Marathon bombings and his first since August 2012 after an achilles tendon injury, Ortiz spoke to the crowd and stated, "This is our fucking city, and no one is going to dictate our freedom. Stay strong."
Ortiz reached several career milestones in 2013, including his 500th career double on July 2 and his 2,000th career hit on September 4. On July 10, Ortiz passed Harold Baines to become the all time leader for hits by a DH with 1689.
On July 27, Ortiz was ejected by home-plate umpire Tim Timmons for arguing balls and strikes against the Baltimore Orioles. After his ejection, Ortiz used his bat to smash a pressbox phone in the dugout. Major League Baseball decided not to suspend Ortiz for the incident.
Ortiz gained several new nicknames from the media and his teammates as a result of his great postseason play such as "Se?or Octubre" and "Cooperstown". He also finished third in Boston's mayoral race that year with 560 write-in votes.