The Scotland international has penned a four-year deal at Craven Cottage after leading the scoring chart's in England's second tier last term with 28 goals to his name.
The reported fee for McCormack will see him become the most expensive player in Championship history, eclipsing the £8m paid by Blackburn Rovers for Jordan Rhodes in 2012.
McCormack is Fulham's fifth signing since their relegation from the Premier League, and is the second striker to arrive at Craven Cottage after Australia international Adam Taggart.
Leeds owner Massimo Cellino claimed last week that he was desperate to keep hold of the Scot after the club rejected offers for his services in January.
However, he has now departed West Yorkshire and joins the likes of Kostas Mitroglou and Hugo Rodallega in Fulham's attacking ranks.
A number of experienced players, including John Heitinga, Steve Sidwell and Damien Duff, have already left the London club as they look to trim their budget for the second tier.
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