A British enthusiast had spent seven years putting together the version of the famous robot using parts from the movies.
A complete R2-D2 made from pieces salvaged from the Star Wars films has sold for $2.76m (£2.13m).
The 43-inch-tall robot was made by an anonymous British enthusiast using retired parts from at least four of the films.
The eventual sale price for the seven-year creation surpassed the highest estimate of $2m.
Brian Chanes, head of acquisitions at Los Angeles auction house Profiles In History, said: "We're very excited to have it because really this is the only one to reach the auction block in the world."
There are rumours that a collector in France has created a similar version of the famous robot but these are as yet unproven.
Mr Chanes added: "It's a high price but, at the same time, you couldn't expect to find a better piece."
The dome was debuted by actor Kenny Baker in the first film, A New Hope, as were the metal details from the body, the auctioneer said.
The legs were from The Empire Strikes Back, the body is from The Phantom Menace and its opening hatch is from Attack Of The Clones, he added.