Morrison — who plays New Directions director William Schuester on the Fox hit — began his performance at Manhattan nightclub 54 Below on Sunday with an acknowledgement of Monteith's death, before changing his show's opening number and performing an a cappella version of the song "What I Did for Love" in honor of Monteith, the New York Times reports.
From the musical "A Chorus Line," "What I Did for Love" was featured in the second season of "Glee."
Referring to Monteith as a brother, Morrison (pictured) conceded that performing the show in the wake of Monteith's death was "awkward," but added, "You guys came to see a show, I came to perform a show, so that’s what we'll do. And we’ll do it in Cory’s honor."
Monteith, who had struggled with substance abuse and entered rehab earlier this year, was found dead in his Vancouver hotel room on Saturday.
Morrison's show "Up Close and Personal With Matthew Morrison," during which he performs classic standards from Broadway musicals, opened Sunday at 54 Below and is scheduled to run through July 17.