Allen recovered in time for the start of the 2007–08 season. In his first game coming out off the injury, Allen scored 4 points and grabbed 5 rebounds during a victory over the visiting Washington Wizards. In his first double-digit scoring output since the injury, Allen recorded 13 points in a win over the New Jersey Nets on November 14. He scored a season-high 20 points in a home game win versus the Memphis Grizzlies. Almost four weeks later, Allen tied his season high during a road victory over the Miami Heat. Allen scored 18 points to go along with 4 rebounds on February 20, during a road loss to the Golden State Warriors. At the end of the regular season, he averaged 6.6 points, 2.2 rebounds, and 1.5 assists in 18.3 minutes over 75 games (11 starts). He substantially contributed to the Celtics' successful playoff run that led to an NBA Finals berth, where they claimed the 2008 NBA Championship after defeating the Los Angeles Lakers in six games.