The star received an honorary doctorate from the university in a ceremony in New York on Wednesday night. He began his studies in 1971, before leaving to pursue an acting career.
"It's been a long haul," he said. "It feels good to have a degree. I'm grateful for the chance to think back."
In his first public remarks since the March death of his wife, Natasha Richardson, Liam apologized for reading from a prepared speech.
"Everyone thinks actors are good public speakers. It's terrifying," he joked.
The actor also explained how his campus career influenced his life.
It was a 1972 campus protest over the Bloody Sunday killings in Northern Ireland that "shook me deeply," Liam revealed.
"The message I took then was, boy, you've got to wake up. You've got to get moving," he said, adding the university taught students to move forward with their lives. "I got on with mine, and I'm still getting on."
In what seemed to be an admission of grief over the loss of his wife, who died suddenly at 45 after a skiing accident, he also discussed the healing power of the arts.
Art "builds from pain, from misery, from a deep-seated hurt," he said, quoting a fellow Queens alumnus, the poet Paul Muldoon.