The reality TV star said in a statement that he won't seek the Republican nomination.
He made his announcement as NBC rolled out its fall lineup. The network is home to Trump's television show, "The Celebrity Apprentice."
Trump has been flirting with a presidential bid for months, traveling to early primary states like New Hampshire, and heckling President Barack Obama from afar.
He is the second Republican in a matter of days to say no to a White House run. Mike Huckabee announced Saturday that he wouldn't seek the presidency.
He also has cancelled what would have been his first foray into South Carolina.
Trump called today to cancel an appearance Wednesday at a Columbia Tea Party rally at the Statehouse.
Organizer Allen Olson said the event will go on without Trump and his group will consider hearing from other presidential hopefuls who want to take Trump's time.
Trump was to headline an awards event that will recognize South Carolina Gov. Nikki Haley, legislators and conservative activists.