On December 6, 2013, the Rangers traded Mashinter to the Chicago Blackhawks for Kyle Beach.[4] On December 13, 2015, Mashinter scored his first NHL goal in a 4-0 win against the Vancouver Canucks.[5] During his tenure in Chicago, Mashinter primarily played with the team's AHL affiliate Rockford IceHogs. Mashinter appeared in a total of 41 games for the Blackhawks, recording 5 points. Mashinter also skated in two games during the 2016 Stanley Cup playoffs.
On September 11, 2017, Mashinter re-joined the Sharks as a free agent, agreeing to a one-year, two-way contract.[6]
As a free agent into the 2018–19 season, on November 12, 2018, it was announced that Mashinter would join the Rapid City Rush of the ECHL.[7] He registered 5 points in 5 games before opting to pursue a European career, agreeing to a contract for the remainder of the year with German outfit ERC Ingolstadt of the DEL on December 5, 2018.[8]