First class passenger Laura Mabel Francatelli, who was one of about 700 people to survive the tragedy in 1912, used the vest before entering a lifeboat.
According to the BBC Auctioneer Andrew Aldridge said he was "ecstatic". He added: "It reflects the ongoing interest and passion for the story of the Titanic, and its passengers and crew."
He previously said the vest was "the only lifejacket from a survivor to emerge at auction in 114 years so it is literally a once in a lifetime opportunity for collectors".
Francatelli and fellow survivors had signed the floation device, which features 12 pockets and is fitted with shoulder rests and side straps.
The jacket sold for hundreds of thousands of pounds more than expected, as it was estimated to sell for between £250,000 and £350,000.
The cushion was originally bought by the friend of London tea importer Richard William Smith, who drowned on the ship when it hit an iceberg in the North Atlantic in 1912.
