[4] On April 2, 2014, the Chicago Blackhawks of the National Hockey League (NHL) signed Johns to a two-year, entry-level contract[5] to begin with the 2014–15 NHL season,[6] but he was immediately assigned to begin his professional career with the Blackhawks' AHL affiliate, the Rockford IceHogs on a professional try-out contract.

[7] On July 10, 2015, Johns and Patrick Sharp were traded by the Blackhawks to the Dallas Stars in exchange for Trevor Daley and Ryan Garbutt.

Having passed his previous season's offensive numbers, he received his first NHL recall by the Dallas Stars and made his debut in a 5–2 victory over the Chicago Blackhawks on March 12, 2016.

[11] On January 18, 2020 Johns played his first game since returning from a post-traumatic headache he suffered during the 2017–18 season, in a Stars defeat against the Minnesota Wild, and on February 3, he scored his first goal in nearly 2 years in a victory against the New York Rangers.

Prior to the pandemic delayed 2020–21 season, Johns was announced to be a non-rostered designated player at the Stars commencement of training camp.