Prior to the 1998–99 season, Detroit traded Knuble to the New York Rangers for a 2000 second-round draft choice (Tomáš Kopecký). Knuble played in all 82 games with the Rangers that season, recording 15 goals and 20 assists. With a month to go in the 1999–2000 season, the Rangers traded him to the Boston Bruins in exchange for Rob DiMaio. After posting 20 points in 82 games in 2000–01 and 14 points in 54 games in 2001–02, Knuble found himself playing left wing on a line with Joe Thornton and Glen Murray beginning in 2002–03. He scored 30 goals and 29 assists in 75 games, good for third on the Bruins.