Kamani, who is executive chairman of the online fashion retailer, sold 35mln of his shares at a price of 285p apiece to institutional investors. He retains a 13.1% holding.
Kane, who stepped back from being joint chief executive earlier this year but remains an executive director, sold 15mln shares at the same price and retaining a 2.7% holding.
Both co-founders have agreed to an 18-month lock-up before selling any more shares in what is AIM's largest company.
Boohoo, which earlier in the week said it had enjoyed “record” sales across the Black Friday weekend and that its debut ranges for newly acquired Karen Millen and Coast have been “very well received”, is worth around £3.5bn, giving it a similar market valuation to Marks & Spencer (LON:MKS) and around £1bn more than one-time 'King of AIM' Asos (LON:ASC).
Shares in the company fell 5% to 280.8p on Thursday morning.