Renowned for his adept power-hitting capabilities, he demonstrates proficiency as a wicketkeeper, coupled with exceptional prowess as a finisher within the contemporary cricketing landscape.

[5] On 2 April 2018, Klaasen joined the Indian Premier League side Rajasthan Royals replacing Steve Smith.

[8][9] In December 2018, Klaasen was bought by the Royal Challengers Bangalore in the player auction for the 2019 Indian Premier League.

[12] In July 2019, he was selected to play for the Glasgow Giants in the inaugural edition of the Euro T20 Slam cricket tournament.

[20] In February 2023, Klaasen scored the second century in the SA20 tournament, making 104 not out from 44 balls for Durban's Super Giants against Pretoria Capitals.

[23] In February 2018, Klaasen was added to South Africa's One Day International (ODI) squad for their series against India, replacing an injured Quinton de Kock.

[28] On 21 February, Klaasen scored his maiden T20I fifty in the second T20I against India which South Africa won by 6 wickets, he was also awarded the man of the match for his 69 runs from 30 balls, which included 3 fours and 7 sixes.

[36] In April 2021, Klaasen was again named as South Africa's T20I captain, this time for their home series against Pakistan, after Temba Bavuma was ruled out due to an injury.

[41] In June 2024, he went on to score the fastest fifty in the history of ICC events finals, men and women, surpassing the record of Alyssa Healy.