The former rivals for the GOP nomination were able to discuss their differences frankly, Kasich told reporters after the session. He explained that he wanted to provide honest advice in a bid to help Trump succeed.
"The man is the president of the United States," he said. "It's sort of like being on an airplane; you want to root for the pilot. If you're on the airplane with the pilot, you don't want the pilot to screw up."
Kasich often offered stinging criticism of Trump during the battle for the GOP nomination last year, suggesting Trump was woefully unprepared for the challenges of the presidency.
Even after Trump bested him for the party's nomination, Kasich remained a critic. He skipped this year's Republican National Convention even though it was held in his own state, and he voted for Sen. John McCain in November rather than Trump.
On Friday, Kasich didn't mask the differences between himself and the President, but he said he worked to avoid making those differences personal.
"I can have my opinions but now it's time to be constructive," he said. "And sometimes being constructive is to not be positive, to make your point, and I'm very glad that I've been able to make my point on this whole business of Obamacare and Affordable Care Act, and I'm going to continue to make it. And if it upsets Republicans in the Congress, that's life."
Kasich said he pressed Trump to maintain an expansion in Medicaid funds under Obamacare, which has helped insure thousands of his state's residents, and called a Republican proposal for a health care replacement "inadequate."
He also detailed his argument to Trump about developing a cohesive foreign policy across the administration, which he said was absent during last week's Munich Security Conference, attended by Vice President Mike Pence and Defense Secretary James Mattis.
"It's important for the administration to speak with one voice," Kasich said. "He listened, acknowledged it, I think was somewhat taken aback, even though he had the vice president and general over there, that sometimes people want to hear from him, and he listened to that."