Cowell earned $75 million between June 1, 2008 and June 1, 2009 to top the list, Forbes reported.
In addition to his Idol compensation, Cowell's claim to the top spot also includes his earnings as producer of NBC's America's Got Talent and the U.K.'s Britain's Got Talent and The X Factor reality series, as well as his fees as a music producer and publisher.
Trump's earnings estimate $50 million, according to Forbes, which added The Celebrity Apprentice continues to attract large sponsors including Zappos.com, Loews Hotels and Chicken of the Sea. In addition, Trump's earning are also tied into products he endorses, speeches and books.
Seacrest ranked third with an estimated $38 million, Forbes reported.
Since Seacrest is widely considered one of the hardest working men in show business, it's no surprise his claim to the list is based on numerous endeavors, including his hosting of the E! News entertainment program, his syndicated KISS-FM radio program, his deals with ClearChannel Radio and the Comcast Entertainment Group, and endorsements for Procter & Gamble products.
In addition, Seacrest's production company's credits -- which include E!'s Keeping Up With the Kardashians, Kourtney and Khloe Take Miami and Denise Richards: It's Complicated reality series -- also factored into his earnings.
The $45 million, three-year deal he inked with Idol's CKX parent company came after the June 1 deadline and will contribute to next year's list, according to Forbes.
Rounding out the Top 10 list are Two and a Half Men star Charlie Sheen ($21 million), The Office star Steve Carrell ($20 million), Deal or No Deal and Howie Does It host Howie Mandel ($15 million), 24 star Kiefer Sutherland ($13 million), Are You Smarter than a Fifth Grader? host Jeff Foxworthy ($11 million), House star Hugh Laurie ($10 million), and CSI: Miami star David Caruso and Grey's Anatomy star Patrick Dempsey (tie, $9 million).
Earning are calculated before taxes, management fees and other costs, and voice-only actors were omitted from the list.