On June 12, 2009, Matsui hit a three-run home run on his 35th birthday, giving the Yankees a 7-6 lead over the New York Mets in the 6th inning. On July 20, he hit a walk-off solo home run with one out in the bottom of the ninth, giving the Yankees their fourth win in a row after the All Star break, their 9th walk-off win, and a tie for 1st place in the division with the Boston Red Sox. A month later, on August 21, Matsui hit two home runs and drove in a career-high seven runs in the Yankees' unusual 20-11 win over the Boston Red Sox at Fenway Park. He became the first Yankee to drive in seven runs in a game at Fenway since Lou Gehrig in 1930. Two games later, Matsui would hit two home runs for his third time in just seven games. Matsui was voted by fans as the MLB Clutch Performer of the Month Presented by Pepsi for August after his performance through the month. On September 19, Matsui hit his 26th home run of the season, breaking the Yankees' record for home runs in a single season by a designated hitter which was previously held by Don Baylor.
In the 2009 World Series, Matsui helped the Yankees defeat the defending champion Philadelphia Phillies, 4 games to 2, by hitting .615 (8 for 13) with 3 home runs and 8 RBI, including tying Bobby Richardson's single-game World Series record (Game 3 of the 1960 World Series) with six RBIs in Game 6. Since the designated hitter position was not used in the three games in Philadelphia, Matsui only started the three games in New York; nevertheless, his performance earned him the World Series Most Valuable Player Award. He became the first Japanese-born player to win the award, as well as the first player to win it as a full-time designated hitter in the World Series. He joined his 1994 Japan Series teammate Dan Gladden (1987 and 1991, Minnesota) as players to have won championships in both North America and Japan. Matsui also became the third player in Major League history to bat .500 or above and hit 3 home runs in the same World Series, joining only Babe Ruth and Lou Gehrig.
On December 16, 2009, Matsui agreed to a one-year deal with the Los Angeles Angels of Anaheim worth $6.5 million. He told Yomiuri Shimbun that he "loved the Yankees the best" but that he no longer felt valued and when his agent called to negotiate, "The Yankees had nothing prepared [in terms of contract conditions]." He made up his mind to sign with the Angels quickly. "I really felt their high expectations of me", he said. "They also acknowledged that I want to give fielding a shot." On Opening Day 2010, Matsui went 2 for 4 with a home run in the Angels cleanup spot. While playing in 145 games for the Angels, he produced a .274 batting average, 21 home runs and 84 RBIs. Matsui returned to free agent status following the close of the season, and on November 23, 2010 the Angels announced that they would not offer him salary arbitration.