Tomkins played junior hockey in the
Alberta Junior Hockey League (AJHL) for two seasons (2011–2013). He was selected in the
2012 NHL entry draft by the
Chicago Blackhawks. After junior career, Tomkins committed to the
Ohio State University and played for their
Buckeyes ice hockey team. After graduation Tomkins signed a one-year contract with the
Rockford IceHogs of the
American Hockey League (AHL), the affiliates of the Chicago Blackhawks, on June 27, 2017. He later signed one-year contract extensions with Rockford in 2018 and 2019. On January 23, 2020, Tomkins signed a two-year, two-way contract with the Chicago Blackhawks and was assigned back to Rockford. However, Tomkins left North American and signed a one-year contract with
Frölunda HC of the
Swedish Hockey League (SHL) on May 28, 2021. On June 2, 2022, he signed a one-year contract with
Färjestad BK of the SHL. Tomkins returned to North America following the
2022–23 SHL season and May 10, 2023, he was signed as a free agent to a two-year, two-way contract with the
Tampa Bay Lightning. Tomkins made his NHL debut with the Lightning on October 15, in a 5–2 loss to the
Ottawa Senators where he made 33 saves. Later during the
2023–24 season, on November 7, 11 years after he was drafted, Tomkins picked up his first NHL career win in a 5–3 victory over the
Montreal Canadiens. Spending the
2024–25 season with the
Syracuse Crunch in the AHL, Tomkins was a co-recipient of the
Harry "Hap" Holmes Memorial Award, the Crunch and the
Laval Rocket having tied for the fewest goals allowed in the league. He had a 12–10–4 record in 26 appearances with the Crunch, with a 2.55 goals against average, a .907 save percentage and three shutouts. Tomkins left the Lightning organization following two seasons, and was signed as a free agent to a two-year, two-way contract with the Edmonton Oilers on July 1, 2025. ==International play==