The deal brings Sotheby's directly into what has been the fastest-growing collectable market of the past decade, and they say they expect to increase their stake in RM as the partnership evolves.
"This long-term investment comes as the more than $2bn market for the finest automobiles continues to grow, presenting increasing opportunities for both companies," said a spokesman.
The partnership has evolved from successful collaborations on a number of occasions in the US and Europe, capped by the November 2013 Art of the Automobile auction in New York, which took nearly $63m in just two hours and featured a new auction record set for a Ferrari 250 LM at $14.3m.
The first RM Sotheby's sale will take place in Amelia Island, Florida, on March 14, with additional auctions in Fort Worth, Texas, Lake Como, Italy, Monterey, California, New York and London. This will put Sotheby's head to head with Bonhams, who have dominated the market in the UK since Robert Brooks took over the company 15 years ago, building on his specialist classic car auction house Brooks, with the backing of Dutch car collector Evert Louwman.
Much of Bonhams' classic and luxury car expertise, led by co-chairman Malcolm Barber, came from Sotheby's previous car department.