The CEO's purchases, registered with the Dutch financial markets authority AFM, were 122,750 shares purchased at an average price around 71.90 euros, Prosus said.
"Buying more Prosus shares reflects my personal conviction that our businesses have had exceptional momentum and that their value is not at all reflected in the stock," Van Dijk said in a statement.
Prosus shares, which often trade in line with the company's biggest asset, a 28.9% stake in Chinese software giant Tencent, have retreated since reaching a high above 109 euros in February. They closed unchanged in percentage terms on Friday at 70.95 euros.
(Reporting by Toby Sterling; Editing by Susan Fenton and Louise Heavens)