"Everything went well, and he's recovering," Marlins manager Mike Redmond said.
During a recent checkup, it was detected that McKeon had blockage in a couple of arteries. Initially, surgery was scheduled for last Thursday, but it was postponed a few days because another patient was in need of more immediate attention.
McKeon has been upbeat throughout the process, and he is expected to need about a month of recovery.
During his stay at the hospital, McKeon has been following the Marlins.
Even on Tuesday morning, he woke up and immediately asked how the Marlins did on Monday night.
"All of us who have been around Jack are relieved that the surgery was successful and he's doing well," Redmond said. "We wish him a speedy recovery. He's such a great guy. We miss Jack and can't wait to get him back."
McKeon is hopeful to be down in Miami to see the Marlins before the All-Star break.
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter