Starting his career in Moss FK, he moved when he was starting lower secondary school to play youth football in Bærum.[1] In November 2018 he signed a two-year contract with the club.[2] He made his debut for Bærum in the Second Division match against Odd 2.[3]
In the beginning of 2021 he joined KFUM.[1][4] The debut came in the First Division match against Jerv.[5] In June 2022 he renewed his contract with KFUM.[6]
He signed a four-year contract with Vålerenga in front of the 2023 season.[7][8] He made his debut in a friendly match against AGF Aarhus.[9] He made his Eliteserien debut on 1 May 2023, in the match against the main rivalLillestrøm SK.[10]
International career
Kiil Olsen was called up for the Norway U21 squad in 2023.[11]