After spending the majority of the season with the Rockford IceHogs, Chicago's American Hockey League (AHL) affiliate, he procured a regular spot on the roster after defenceman James Wisniewski's trade to the Anaheim Ducks.

[1] On 9 July 2010, shortly after the end of the season, Hjalmarsson signed a four-year, $14 million offer sheet with the San Jose Sharks.

[citation needed] During 2012–13 NHL lockout, Hjalmarsson played in Italy's Serie A and in the IIHF Continental Cup with HC Bolzano.

During game 7 of the Western Conference's semifinal series against the Detroit Red Wings, with the score tied at 1–1 late in the third period, Hjalmarsson scored what appeared to be a go-ahead goal with 1:47 left in regulation time, but referee Stephen Walkom called offsetting penalties on Detroit's Kyle Quincey and Chicago's Brandon Saad just before the puck went in, so the goal was disallowed.

After the 2016–17 season, his 10th year with the Blackhawks, Hjalmarsson's tenure with the club came to an end as he was dealt to the Arizona Coyotes in exchange for Connor Murphy and Laurent Dauphin on 23 June 2017.