Investec did not go ahead with a planned public offering of 10% of its shares because of the recent falls in markets, but management planned to increase its shareholding over time, Hendrik du Toit told Reuters.
Shares in Ninety One opened at 135 pence per share on the London Stock Exchange, before rising to 150 pence in early trades. Investec had originally planned to sell a 10% stake somewhere between 190 and 235 pence per share.
This would have given the company a market capitalisation of up to 2.26 billion pounds ($2.79 billion).
(Reporting by Carolyn Cohn and Abhinav Ramnarayan)