Pataki, who suspended his own bid to be the Republican presidential candidate last December, made the announcement at the New York State Republican Gala at Manhattan's Grand Hyatt Hotel.
"I am proud to endorse Governor John Kasich to be the next president of the United States," Pataki told reporters. "First of all, as a Republican we need to win this race. And Governor Kasich is the only one who right now, who not just beats Hillary Clinton, he trounces Hillary Clinton. And he will win this race if he gets the nomination of the Republican party. Secondly, once he wins the election, we need somebody who can bring Americans together, not just Republicans but Republicans, Democrats and independents, and straighten out our finances, grow our economy, keep us safe."
Pataki added, "Governor Kasich has shown he can do that in one of the most important states in this country, and I have no doubt he can do that in Washington. He will win this race if he is the Republican nominee, he will bring Americans together and he will successfully lead this great country so I am honored to endorse Governor Kasich."
During Thursday's "Powerhouse Politics" podcast, Pataki told ABC News' Chief White House Correspondent Jonathan Karl and Political Director Rick Klein, he was concerned GOP front-runner Donald Trump would destroy the Republican party.
“I think Donald Trump would drive the Republicans off a cliff if he’s our nominee,” Pataki, one of Trump’s biggest Republican critics, told Karl and Klein, adding he’s doing everything in his power to prevent a Trump nomination. “I am encouraging people to come out and vote ... whether you like [Ted] Cruz or whether you like [John] Kasich, your vote counts.”
When Pataki bowed out in December, he said, "If we’re truly going to make America great again, we need to elect a president that will do three things: confront and defeat radical Islam, shrink the power and size of Washington, and unite us again in our belief in this great country," Pataki said at the time.
In January, Pataki endorsed former presidential candidate Marco Rubio, who has since dropped out of the race as well.
Pataki slammed GOP front-runner Donald Trump at the time.
"Donald Trump is dividing us," Pataki said. "Marco Rubio is going to bring us together."