The South African business, which owns 20 retail brands and has a footprint of more than 2,700 stores, has taken a "substantial majority" stake in the British firm, headed by Jane Shepherdson sine 2008.
Foschini, which bought Phase Eight last year, has acquired all 46 stores and the online business for an undisclosed sum, said the move would "provide significant investment for Whistles and opportunities for the brand to continue to further develop its online presence, grow its retail portfolio and accelerate international expansion plans".
Former Topshop boss Shepherdson - who has turned the business around from its frumpy former image to one of cutting edge fashion, with collections at London Fashion Week and launching a menswear division - has kept her stake and will continue to run the business after the deal goes through. Chairman Peter Davies has sold his stake.
Shepherdson said: "We very much look forward to working with the TFG team to continue to build on the success of Whistles and take it to the next stage of its evolution."
Foschini Group chief executive Doug Murray added: “Whistles is a brand that we have long admired, for which we believe there is a significant global opportunity for growth. We look forward to working with the team to further develop the brand”