He played in the National Hockey League (NHL) for the Boston Bruins, Colorado Avalanche, New York Rangers, Toronto Maple Leafs, Pittsburgh Penguins and the Buffalo Sabres.

After two seasons with the USDP, and showing potential as a two-way puck-moving defenseman he was recruited to play collegiate hockey with the University of Michigan in the CCHA.

As a sophomore in the 2004–05 season he scored his first career hat-trick, in an 8–3 victory over Bowling Green State on December 10, and was honored as the NCAA National Offensive Player of the Week.

Hunwick received the same Second All-Star accolade while serving as an alternate captain in 2005–06, when he recorded a personal-best 11 goals and 30 points in 41 games to finish second among Wolverines D-men.

[9] After spending a month with Providence, Hunwick was recalled by Boston and played his first NHL regular season game in a 2–1 victory over the Buffalo Sabres on November 10, 2007.

[12] Establishing a puck-moving role among the Bruins defense corps, Hunwick amassed a career-high 21 assists and 27 points in 53 regular season games.

In the 2010–11 season, with the Bruins in need to reduce roster salary, Hunwick was traded to the Colorado Avalanche in exchange for Colby Cohen on November 29, 2010.

[19] On July 1, 2014, Hunwick ended his four-year tenure with the Avalanche by signing as a free agent to a one-year contract with the New York Rangers.

[22] In concluding a successful two-year tenure with the Maple Leafs, Hunwick left as a free agent and signed a three-year $6.75 million contract with two time reigning champions, the Pittsburgh Penguins, on July 1, 2017.

[23] On June 27, 2018, Hunwick, along with teammate Conor Sheary, was traded to the Buffalo Sabres for a fourth-round pick in the 2019 NHL Entry Draft.