Matthew Morrison paid special tribute to Cory Monteith on Sunday during his scheduled show at 54 Below in New York City.
He opened the concert with comments about his fellow "Glee" co-star, who died Saturday at age 31.
Calling Monteith a "brother," Morrison, 34, spoke about losing Monteith way too soon, reports The New York Times. He then performed an a capella version of "What I Did for Love" from the musical, "A Chorus Line," which appeared on the second season of the Fox series.
After the song dedication, Morrison said it felt "awkward" to perform under the circumstances, but said, "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."
A source told Us Weekly, "He was very emotional on stage. It was difficult for him to get up to perform, but he did not want to disappoint anyone."
Morrison and Monteith starred together on "Glee" since the show's inception in 2009 -- Morrison as teacher and glee club instructor, Mr. Shuester, and Monteith as Finn Hudson, a football player, student and glee club member.
There was an outpouring of support following Monteith's death on Saturday, with celebrities taking to Twitter to express their condolences.