His leadership qualities led to several appointments above more experienced players and more successful batsmen: he first captained Western Province at the age of 23; he was selected as vice-captain of the touring team to Australasia in 1963–64 at 26 despite having never played a Test; he captained the team to England in 1965 having played only 7 Tests and making only 198 runs at an average of 24.75.

Wisden's report of the 1965 series ranked him as equal second (with Tiger Lance) in the team after Colin Bland 'for general brilliance in the field'.

Christopher Martin-Jenkins described van der Merwe as 'a thoughtful and shrewd captain who inspired a zealous team-spirit'.

[7] The first player of Afrikaner background to captain South Africa, he wrote the Afrikaans cricket book Wenkrieket So Word Dit Gespeel in 1967.

Van der Merwe died in Port Elizabeth in January 2013, aged 75, having been in poor health prior to his death.