Following his selection by the St. Louis Blues in the 2018 NHL entry draft, Hofer was signed to a three-year, entry-level contract on March 22, 2019.[5] During the 2021–22 season, Hofer was recalled from AHL affiliate, the Springfield Thunderbirds, and made his NHL debut on November 5, 2021 against the San Jose Sharks, where he tallied an assist in the 5–3 win. Upon making his debut at the age of 21 years, 97 days, he became the youngest goaltender to win his NHL debut with the Blues.[6] While playing with the Thunderbirds during the Calder Cup playoffs, Hofer scored a goal against the Wilkes-Barre/Scranton Penguins on May 12. This was the first instance of an AHL goaltender physically scoring a goal.[7]
Entering his final year of his entry-level contract in 2022–23, Hofer was re-assigned to continue his development in the AHL. He enjoyed success with the Thunderbirds, and at the end of the season was named to the league's Second All-Star Team.[8] He played the third-most minutes of any AHL goaltender that season.[7]
On January 3, 2023, Hofer was signed by the Blues to a two-year, one-way contract extension worth $1.55 million.[9]
Hofer was invited to make his international debut for Canada with the national junior team after attending the selection camp for the 2020 World Junior Ice Hockey Championships.[2] He was not initially Team Canada's starting goaltender, that position occupied by Nico Daws. After Daws allowed four goals on the first 17 shots of the team's second game of the tournament against Russia, Hofer relieved him midgame. He allowed two goals on 22 shots, and was thereafter given the net.[3] Team Canada went on a deep run to the championship final, a rematch with Russia, where Hofer made 35 saves on 38 shots in Canada's gold medal win. He was given the IIHF directorate award for Best Goaltender of the tournament, as well as named to the events Media All-Star Team.[10]
Following his successful 2022–23 AHL season, Hofer was invited to join the senior national team at the 2023 IIHF World Championship. He made his first appearance on May 17 against Kazakhstan, where he allowed one goal on 17 shots in Team Canada's 5–1 win.[11] He ultimately appeared in two of ten tournament games, managing a .925 save percentage, while Team Canada won the gold medal.[12] The following year, he rejoined the team for the 2024 IIHF World Championship as one of its three goaltenders, alongside Blues teammate Jordan Binnington and former World Junior teammate Daws.[13]
