Monteith, who died of a heroin and alcohol overdose on July 13, played the sensitive high school star quarterback who turned singer for the hit FOX show, now in its fifth season.
The episode opened with the cast singing Seasons of Love before the characters were asked by their teacher Mr. Shue, played by Matthew Morrison, to perform tracks that remind them of Monteith's character.
Glee's creator Ryan Murphy wrote the episode and chose not to reveal how Hudson had died - instead it picked up the storyline three weeks after his funeral.
Former Glee actors Amber Riley, Mark Salling and Harry Shum, Jr. returned for the tribute episode, but Monteith's on-and-off-screen girlfriend Lea Michele didn't appear until the last 15 minutes of the episode to sing an emotional rendition of Bob Dylan's Make You Feel My Love.
Following the broadcast, Glee star Kevin McHale tweeted, "Tonights Glee was made out of a lot of love & a lot of tears by our incredible crew, cast & creators for our friend Cory. We miss you Cory", and Shum, Jr. adds, "Forever in our hearts. #finnhudson."