[4] On 28 June 2014, Polák was traded to the Toronto Maple Leafs in exchange for defenseman Carl Gunnarsson and a 2014 fourth-round draft pick (Ville Husso).

On 22 February 2016, Polák was traded to the San Jose Sharks along with Nick Spaling in exchange for second-round draft picks in 2017 and 2018, as well as forward Raffi Torres.

However the Maple Leafs exceeded expectations and found themselves within the playoff race come trade deadline, leading to Polák remaining with the team in a bid to make the post-season.

On 23 March 2017, Polák was suspended for the first time in his career for two games as the result of a hit from behind on Columbus Blue Jackets forward Oliver Bjorkstrand a few nights earlier.

[8] Once he returned, Polák assisted the Maple Leafs in clinching a playoff spot; the first time the team has achieved the feat in a full season since 2004.

During the NHL's hiatus, Polák agreed to a three-year contract to return to his native Czech Republic with original club, HC Vítkovice, beginning from the 2020–21 season on 15 June 2020.