Duncan Ford, who was 16, was seen falling from Wearmouth Bridge, Sunderland, on Thursday.
The Newcastle actor played a new character called Alan and had filmed three episodes to be screened in the new series this year.
A statement from the BBC said: "The entire team at Byker Grove are shocked and devastated at the news of Duncan's death."
Police say his death isn't suspicious.
Byker's been going since 1987 and launched stars like Ant and Dec and Donna Air, who all appeared in the show in the 1990s.