Mathias Kjølø

Kjølø was born in Oslo and played youth football with Kjelsås until 2016, after which he left for Vålerenga.

PSV

After six months with Vålerenga, he was sent on loan to Dutch club PSV Eindhoven, who then signed him to a permanent deal in 2018. He made his professional football debut for the reserve team Jong PSV in the second-tier Eerste Divisie on 13 January 2020 in a 0–0 draw at home against Jong Ajax. On 16 October 2020, he signed a two-year extension to his contract, keeping him at PSV until the summer of 2023. He made his first-team debut for PSV on 8 November 2020 in a 3–0 Eredivisie win over Willem II, coming on as a substitute for Ibrahim Sangaré in the 88th minute.

Twente

On 8 June 2022, PSV announced that Kjølø had signed a long-term contract to join FC Twente ahead of the 2022–23 season.

Rosenborg

On 31 August 2026, Kjølø signed a four-and-a-half year deal with Rosenborg.

Kjølø played for various Norwegian national youth teams between 2017 and 2019. On 12 October 2021, he made his debut for the Norway national under-21 team in a 3–0 win over Estonia as a 78th-minute substitute for Johan Hove.

As of match played 19 September 2026