The Appaloosa Management CEO on Monday told CNBC's Squawk Box he is voting for the Democratic nominee in her bid for the White House.
He said he would be voting Republican down the rest of the ticket.
Tepper described the uncertainty that would surround a Donald Trump presidency.
"This is a guy that has to remind himself on a podium to stay on message," he said, suggesting Trump may need to remind himself not to "push the red button" if elected president.
He also criticized Trump for not donating "one dime" to benefit dinners following Hurricane Sandy or 9/11.
"You can't tell me this is a charitable, generous person," he said.
While Trump claims to be an "angel of light," Tepper said he is actually the "father of lies."
Tepper had previously referred to one presidential candidate as "demented, narcissistic, and a scumbag," without identifying which candidate he meant. This is the first time he has officially given his support for Clinton.
"You have one person with questionable judgment, and the other person that may be demented, narcissistic, and a scumbag," Tepper said in October. "I'm not saying which one is which. You can make your own decision on that."
He said at the time he had not provided financial support to either presidential candidate.