A wholly owned subsidiary of HCI has acquired 34.5m Johnnic ordinary shares at an average price of R9.00 per share, amounting to a total cash consideration of R311.2m.
This was funded out of existing cash resources, the company added.
JSE-listed Johnnic has interests mainly in the gaming industry after having unbundled most of its other holdings in the telecommunications, media and other sectors, in the past year.
HCI, meanwhile, has interests in IT, telecommunications, media and broadcasting, interactive gaming and financial services.
Explaining the rationale behind the acquisition, HCI said it considered it to be "opportune" as it furthered HCI's ongoing gaming strategies.
Johnnic's share price was up 3.3% or 30 cents on the day so far, last quoted on the JSE Securities Exchange SA at R9.50 from R9.20 at Friday's close.