Cory, who played loveable high school quarterback Finn Hudson in the US teen comedy musical, was found dead in Vancouver, Canada, in a hotel room on 13 July 2013. An autopsy later ruled the 31-year-old's death was due to an overdose of heroin and alcohol.
The third episode of the fifth season, titled The Quarterback, shows the McKinley High family join together to remember the life of Finn.
In the emotional preview clip, Finn's friends hold a shrine outside his locker and Lea Michele's character Rachel Berry is seen in tears as she is being consoled by high school teacher Will Schuester, played by Matthew Morrison.
At the time of reading the script, Jane Lynch, who plays tough-talking cheerleading coach Sue Sylvester, described the episode as the "most beautiful thing".
Following Cory's death, show producers announced that Glee would write out his character in an episode that tackles the actor's real life struggle with drug use.
A final coroners report this week revealed that Cory's death was accidental, resulting from intravenous heroin use combined with alcohol.
Cory's tribute episode follows on from two Beatles specials that the cast filmed for the brand new season.
Watch the preview clip below: