James will play Seb and he will also be joined by Dudley Sutton, who will play his father William. Dudley first appeared as a short-term character 15 years ago.
James, who played Finn in Channel 4's Hollyoaks, said: "Having taken a five-year break from acting to concentrate on stand-up comedy, I am really looking forward to getting back on the horse.
"It will be great to join the cast of Emmerdale and Seb will be my first time playing a northerner."
Dudley, 80, who starred in the BBC's Lovejoy series, first appeared in Emmerdale as a down-and-out. William reappears when Ruby Haswell, played by Alicya Eyo, applies to work as his carer, but doesn't realise he's the father of her former boyfriend, Seb.
Dudley said: "This will be my second appearance in Emmerdale as I appeared in 1997 as a tramp!
"It's great to be back in Yorkshire and I have fond memories of filming the Beiderbecke trilogy in the same building as Emmerdale is now filmed."
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