The image of Brigitte Bardot, from 1963, was an early painting by Gerald Laing, who passed away in 2011.
It was sold at Christie's for £902,500 - a record for the artist's work.
The artist, who was born in Newcastle-upon-Tyne, sold the painting to a private collector in 1963 for £40 when he was at art school at London's St Martins School of Art.
Although it had been widely exhibited, it had remained with the same owner until the sale on Thursday.
The painting was one of the first where the artist used monochrome dots, a trademark of his work.
Laing considered it to be one of his most significant pieces.
Laing lived in a restored castle on the Black Isle in the Scottish Highlands until his death in 2011.
He spent much of the 1960s working in New York City.
He moved to the Highlands in 1969, buying and restoring the previously ruined Kinkell Castle.
The sale also saw a painting by Francis Bacon become the most valuable piece of artwork ever sold by Christie's in Europe after going under the hammer for a record £42.2 million.
The 6ft-tall canvas of Bacon's former lover and muse George Dyer was estimated at £28 million. It was sold to an anonymous telephone bidder.