[2] He made his List A debut for the Netherlands against Zimbabwe on 24 June 2017,[3] having played club cricket in England and New Zealand.
[10] In December he was named in the squad for the 2018–19 Oman Quadrangular Series, playing in all three of the Netherlands' matches during the tournament.
[1][12] He made his first-class debut on 31 March 2019 for Kent against Loughborough MCCU, as part of the Marylebone Cricket Club University fixtures.
[15] In the 2018/19 northern hemisphere winter he played in Australia for Monash Tigers in Victorian Premier Cricket.
[19] Having not made an appearance for the club in 2024 due to a back injury sustained on international duty, Klaassen signed a new one-year white-ball contract with Kent in December 2024.