The price was an record for Richter and also the second highest at auction for any living artist - only behind Jeff Koons's sculpture Balloon Dog (Orange) which fetched $52m (£34m) at Christie's New York in November 2013.
Abstraktes Bild from 1986 was a 9ft 10in x 8ft 3in (3.01 x 2.51m) oil on canvas which had been acquired by the vendor from Sotheby's in 1999. Back then it made $607,500 - a record for an abstract piece by the artist at the time. It subsequently hung in the Ludwig Museum in Cologne.
With the Richter market expanding massively in the last 16 years, it reappeared here with a £14m-20m estimate. Two determined phone bidders battled it out on the night with one of them, an American private collector, aggressively increasing the increments at £2m a time. There were gasps in the room as the bidding rose from £18m to £20m in one hit, and then again as the price jumped from £23m to £25m.
"I need to sit down," said auctioneer Oliver Barker after banging his gavel down to a round of applause.
Overall, the sale posted a strong performance and the premium-inclusive total of £123.5m was the highest for a Sotheby's sale of Contemporary Art in Europe. Sixty-five of the 75 lot sold on the night (87%).
Francis Bacon's Two Studies for Self-Portrait got away at £13m to European private collector on the phone. Although it drew little interest and sold on low estimate, the sum was well above the price it sold for last time it appeared at auction when it made £353,500 in the same rooms in December 1993.
The Contemporary art auction series in London continues with Christie's hosting their evening sale tonight.