AP Photo/J. Scott Applewhite
"Donald Trump and I have talked at great length about things such as the proper role of the executive and fundamental principles such as the protection of life," Ryan wrote. "The list of potential Supreme Court nominees he released after our first meeting was very encouraging."
He continued: "Through these conversations, I feel confident he (Trump) would help us turn the ideas in this agenda into laws to help improve people's lives. That's why I'll be voting for him this fall."
There was speculation over whether Ryan would vote for Trump after he said in an interview with Jake Tapper last month that he was not yet ready to support the billionaire real estate mogul.
Ryan and Trump met to discuss areas of common ground on May 12, but Ryan said afterward that it was too soon for an endorsement. Ryan's spokesman, Brendan Buck, tweeted on Thursday after Ryan's column was published that "we're not playing word games, feel free to call it an endorsement."
Ryan noted on Twitter and in The Gazette that uniting the GOP and keeping democratic frontrunner Hillary Clinton out of the White House ultimately outweighs his differences with Trump.
I'll be voting for @realDonaldTrump this fall. I'm confident he will help turn the House GOP's agenda into laws. https://t.co/LyaT16khJw
"A Clinton White House would mean four more years of liberal cronyism and a government more out for itself than the people it serves. Quite simply, she represents all that our agenda aims to fix," Ryan wrote.
"It's no secret that he [Trump] and I have our differences," he continued. "I won't pretend otherwise. And when I feel the need to, I'll continue to speak my mind. But the reality is, on the issues that make up our agenda, we have more common ground than disagreement."
Ryan's column was published as Clinton gave a highly-publicized foreign-policy speech slamming Trump on Thursday.