The actress will be joined by Sterling K Brown, Ryan Michelle Bathe, Uzo Aduba, Aisha Hinds, Kendrick Sampson and Jeremy Pope.
The stars will re-enact the season three episode The One Where No One’s Ready.
The event, held via Zoom, will benefit When We All Vote, an organisation attempting to increase voter registration numbers.
Friends fans were treated to a mini reunion during Sunday’s Emmys, when Jennifer Aniston was joined at home by her former co-stars Courteney Cox and Lisa Kudrow.
The long-awaited reunion show is set to arrive on the HBO Max streaming service but has been delayed due to the coronavirus pandemic.
Friends is one of the most popular TV shows ever but has attracted criticism for a lack of diversity among the cast.
All six of its main stars were white, as was the majority of the supporting cast.
In June, Friends co-creator Marta Kauffman reportedly became tearful when asked about the issue.
Speaking as part of a virtual panel discussion in June, she said: “I wish I knew then what I know today. Sorry, I just wish I knew then what I know now. I would’ve made very different decisions.
“I mean we’ve always encouraged people of diversity in our company, but I didn’t do enough and now all I can think about is what can I do?”
The Friends edition of the Zoom Where It Happens episode is set to take place at 2am Wednesday UK time.
With reporting by Press Association.