Boychuk was born in Canada. As a youth, Boychuk played in the 1997 Quebec International Pee-Wee Hockey Tournament with a minor ice hockey team from Edmonton. Boychuk was drafted 61st overall in the National Hockey League's 2002 Entry Draft by the Avalanche of Colorado. Prior to being drafted, he played with the Western Hockey League's Calgary Hitmen. Boychuk made his professional debut with the Hershey Bears in the 2004–05season. Boychuk spent the next four years in the Avalanche organization playing primarily for their American Hockey League affiliates. He made his NHL debut in the 2007–08 season on January 5, 2008, against the New York Islanders. Boychuk made his debut as a forward playing on the wing rather than his usual defenceman position. in 2010 On June 24, 2008, Boychuk was traded to the Boston Bruins in exchange for Matt Hendricks. He was assigned to their AHL affiliate, the Providence Bruins, to start the 2008–09 season and in his first week was named "AHL Player of the Week." On December 1, 2008, Boychuk was recalled to Boston and made his Bruins debut in a 3–1 victory over the Tampa Bay Lightning on December 4, 2008. Boychuk was then returned to Providence for the rest of the season, where he played a break-out season, capturing the Eddie Shore Award by leading the league with 20 goals and 45 assists among defenceman and being named to the AHL's First All-Star Team. On July 1, 2009, Boychuk secured his first one-way contract when he re-signed with the Bruins for the 2009–10 season. After initially making the Bruins opening night roster, Boychuk was primarily a healthy scratch in the first months of the season. After returning from a conditioning assignment in Providence, he established himself within the Bruins as a two-way defenceman to finish with 15 points in 51 games to earn a two-year contract extension on June 24, 2010. in November 2017. He was a member of the Bruins when they defeated the Vancouver Canucks to win the 2011 Stanley Cup Finals. The following season, Boychuk was rewarded with a three-year contract extension to remain a fixture on the Stanley Cup-winning Bruins blueline. Despite an inability to successfully defend the Stanley Cup, Boychuk produced 15 points in 77 games. During the 2012–13 NHL lock-out, Boychuk ventured to Europe and signed a temporary contract in Austria with EC Red Bull Salzburg of the EBEL on November 16, 2012. He scored two goals and posted eight points in 15 games before he returned to the Bruins for the shortened 2012–13 season. On October 4, 2014, due to salary cap constraints, Boychuk was traded to the New York Islanders in exchange for two second-round draft picks in the 2015 and 2016 NHL Entry Drafts, as well as a conditional third-rounder in the 2015 Draft. In his Islanders debut, Boychuk scored a goal and two assists against the Carolina Hurricanes. On March 12, 2015, he signed a seven-year, $42 million contract extension with the Islanders, lasting through the 2021–22 season.
