The 27-year-old has penned a four-year deal at Craven Cottage, with the option of a further 12 months.
The Scotland international scored 29 goals last season to finish as the top scorer in the Championship.
McCormack netted 58 times in 158 appearances for Leeds after joining them from Cardiff City in 2010.
"Fulham Football Club is delighted to announce the signing of Ross McCormack from Leeds United for an undisclosed fee," a statement on the club's official website read.
McCormack has become Fulham's fifth signing this summer.