Beltrán played for Puerto Rico in the 2006 World Baseball Classic, joining Carlos Delgado, Bernie Williams, Javier Vázquez, Iván Rodríguez and others on the team managed by St. Louis Cardinals third base coach José Oquendo. His 2006 season was an upgrade on his first year in New York. Boosted by 10 home runs in May, he surpassed his home run total from the previous year before the season was half over. Beltrán's performance secured him a spot in the 2006 All-Star Game, his third. Five other Mets joined him, including three as starters. Beltrán was a standout for the NL as the only batter with multiple hits, along with two stolen bases. He scored the go-ahead run that gave the National League a 2–1 lead in the third inning, though the American League won the game. He hit grand slams in consecutive games on July 16 and 18, becoming the 23rd player to do so. Another grand slam at the end of July made him only the third Met to hit three in one season. Beltrán continued to produce with a walk-off home run against the St. Louis Cardinals on August 22, off Cardinals closer Jason Isringhausen. It was Beltrán's second walk-off of the season, following a 16th-inning gamewinner against the Phillies.