The special broadcast will take place in October to celebrate the ITV1 soap's milestone.
Show stars Jason Merrells and Gaynor Faye, who play Macey siblings Declan and Megan, revealed the news to Digital Spy's showbiz reporter Anna Williamson on the red carpet at the British Soap Awards at the weekend.
Merrells commented: "We've got the 40th anniversary of the show [coming up], it's got a live ep so everybody's positive about that. It should be pretty good, the stories are getting stronger and everything's hotting up."
Meanwhile, Faye predicted that the live broadcast would feature "fireworks".
She explained: "None of us actually know whether we're involved or not… I think they're going to try and involve everybody because it's such a celebration and such an achievement to get to the 40th year. So fingers crossed everybody will be involved."
In a statement released exclusively to Digital Spy this afternoon (May 1), an Emmerdale spokesperson commented: "In celebration of its 40th birthday, Emmerdale will be going live for the first time for an episode in October.
"Series producer Stuart Blackburn has already confirmed that the anniversary will be a week long celebration of 'must see TV featuring two weddings, one of which will be the most unexpected we have ever seen, plus the birth of two babies'.
"Further highlights and the date and length of the episode will be announced on a separate occasion."
Soap fans saw Coronation Street go live for its 40th and 50th anniversaries in 2000 and 2010 respectively, while EastEnders broadcast a live special for its 25th birthday.
> Emmerdale boss teases "spectacular" anniversary plans
> Emmerdale: Character teasers, gossip from producer Stuart Blackburn
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