Fox Entertainment Chairman Kevin Reilly declined to specify how the character would exit, saying he couldn't confirm Finn would be felled by drugs.
Monteith, 31, was found dead in a hotel room in Canada last month. Tests showed his death was caused by a mixture of heroin and alcohol.
Fox intends a "celebration" of a vibrant young man, Reilly told the Television Critics Association. "You see some people struggling with addiction, it's clear: 'He was dark, she was always a partier.' Cory was a big, open, wonderful life force. He wasn't like that."
But Reilly said that while Monteith was open about his past — the actor had spoken publicly of his addiction struggles — he wasn't "as open about it in the present."
Working on details
Reilly said the show's producers are working out the details for the episode. Public service announcements related to Monteith's death are planned.
Lea Michele, the Glee star who played Finn's girlfriend and was in a relationship with Monteith, has been "a pillar of strength in all this," Reilly said.
Proceeds from music sales for the tribute will go into a fund in Monteith's honor.
Episode three of new season
The episode will be the third aired in the new season of Glee, which begins on 26 September. The first two episodes will be upbeat celebrations of Beatles songs, Reilly said.
Glee will take a break of several weeks after the Monteith tribute as Fox airs baseball's World Series.
Glee, about a high school's glee club and its graduates, will be in its fifth season. Its return was delayed a week by Monteith's death.