Kelemen was a member of HKM Zvolen's academy of the Slovak Extraliga before making his professional debut for the team during the 2016–17 season. On 2 July 2018, he signed for HC Slovan Bratislava of the Kontinental Hockey League (KHL)[1] but would play just two games during the 2018–19 KHL season[2] before returning to HKM Zvolen. Kelemen signed a new contract with Zvolen on 17 June 2020.[3] In the following 2020–21 season, Kelemen enjoyed a breakout season in recording career-high marks of 19 goals and 19 assists for 38 points in 45 regular season games. He contributed six post-season goals through 11 games to help HKM Zvolen claim the championship.[4]
On 1 May 2021, Kelemen left Zvolen to continue his development and signed a contract with Czech Extraliga (ELH) outfit, BK Mladá Boleslav.[5] Quickly adjusting to the ELH in the 2021–22 season, using his size and scoring touch, Kelemen notched five goals and 18 points through 44 regular season games. He increased his production in the playoffs, helping Mladá Boleslav reach the semi-finals and finishing with nine goals and 12 points in just 14 post-season games. In recognition of his impressive year, Kelemen was selected as the Czech Extraliga's Rookie of the Year.[4]
Kelemen began the 2023–24 season with Tucson. He was recalled by Arizona on 13 November 2023.[10] He made his NHL season debut on 18 November playing on the fourth line with Alex Kerfoot and Liam O'Brien.[11] He registered his first point of the NHL season on December 11, assisting on Michael Kesselring's second period goal in a 5–2 loss to the Buffalo Sabres.[12] He was returned to Tucson in December having played in ten games, recording just the one point.[13] Shortly after the end of the 2023–24 regular season, the Coyotes' franchise was suspended and team assets were subsequently transferred to the expansion Utah Hockey Club; as a result, Keleman became a member of the Utah team.[14]
On 3 July 2024, Keleman signed a one-year, two-way contract with Utah.[15] To start the 2024–25 season, he was assigned to continue his tenure with the Roadrunners. He made 11 appearances and posted six points before being loaned by Utah to HC Dynamo Pardubice of the Czech Extraliga on 26 November 2024.[16]
^"Mladík Miloš Kelemen v Kádri Slovana" [Young Miloš Kelemen in Slovan's Squad] (in Slovak). HC Slovan Bratislava. 18 July 2018. Retrieved 22 November 2023.