The actor, best known for his role as Kerr Avon on the sci-fi show, will play Alan Turner's (Richard Thorp) old friend Eddy Fox in ten episodes of the Yorkshire-based programme.
Eddy, described as a 'funloving' character, will make his first appearance in July when he arrives in the Dales on a trike.
Darrow told The Sun: "I am delighted to be appearing in Emmerdale. My character Eddy's going to be great fun to play. I'll get to ride around the Dales on my trike in my leathers. I'll be like Marlon Brando.
"I'm also really looking forward to catching up with my old pal Richard Thorp. We used to work together way back on Emergency Ward 10."
The 68-year-old also played Doctor Who's Captain Hawkins in the '70s. More recently, he has appeared in Little Britain and Law and Order: UK.