The portrait of a young Chinese girl with green-hued skin and ruby lips was expected to fetch up to 500,000 pounds by the Auction house Bonhams.
It was bought by British businessman and jeweller Laurence Graff and will go on public display in South Africa, BBC News reported.
According to a Bonhams representative, the painting will be exhibited, alongside the rest of the diamond retailer's art collection, at the Delaire Graff Estate, near Stellenbosch in the Western Cape.
Tretchikoff, who grew up in Russia and Shanghai, eventually settled in South Africa in 1946 and completed the Chinese Girl in Cape Town in 1953.
His model was Monika Sing-Lee, then 17, whom he spotted working at her uncle's launderette in Sea Point, Cape Town.