After two successful performances in the ELH, Rittich was signed to a one-year, two-way contract on 10 June 2016, by the Calgary Flames of the National Hockey League (NHL).

[3] Rittich made his NHL debut against the San Jose Sharks in the third period of the Flames' final regular season game of the year.

[8] On 10 November 2018, Rittich earned his first shutout in the NHL against the Los Angeles Kings in a 1–0 win with the only goal scored by Travis Hamonic.

[16] Following a lone season with the Predators, Rittich left as a free agent and was signed to a one-year, $900,000 contract by the Winnipeg Jets on 13 July 2022.

[17] Serving as the backup to Jets starting goaltender, Connor Hellebuyck, Rittich made 21 appearances in the 2022–23 season collecting nine wins.