After the Nazis branded his paintings "degenerate art", Beckmann and his wife, Mathilde, known as "Quappi", fled Germany in 1937. Waiting in Amsterdam for years for a visa to the United States, Beckmann worked under adverse circumstances.
In the portrait, Beckmann departed from his usual dark colours and painted himself wearing a yellow fabric. His distant gaze, meditation-like pose and almost bald head are reminiscent of a Buddhist monk.
The auction house has said there are no questions over the artwork's provenance, as the artist gave it to his wife who loved it so much she kept it until she died in 1986.
Eventually a private collection in Switzerland purchased the painting before entrusting it to Villa Grisebach.
A spokesperson for Grisebach said the successful bid, from Switzerland, was 20 million euros and the remainder of the price covered fees. There had been competition from five countries.