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.
Auctioneers hope the sale, which Grisebach said was the second highest price fetched globally for an artist's self-portrait, will boost Germany's art market, which trails New York, London and Paris.
In 2018, Villa Grisebach obtained the highest auction price to date for a painting in Germany when it sold Max Beckmann's 'The Egyptian' for 5.5 million euros.
