The West End star will play bad boy Danny Houston, the best friend of Brendan Brady (Emmet Scanlan). Danny is also Cheryl Brady's (Bronagh Waugh) silent partner in Chez Chez.
However, Cheryl quickly realises that Danny is not someone she wants to be in business with as his arrival causes trouble for the residents of the Channel 4 soap. He takes a shine to Jacqui McQueen (Claire Cooper), leaving Rhys Asworth (Andy Moss) - but also playing with fire as Jacqui is dating Brendan. The McQueen soon finds herself embroiled in Danny and Brendan's shady world.
Day said: "I've really enjoyed filming with Hollyoaks and I'm excited about coming back. Danny is the type of character any actor would kill to play and the part has been made even better as I'm working with great talent such as Claire, Emmett and Bronagh."
He added: "I've been a fan of the show for some time and this is a very exciting time with the show’s recent reinvention. I’m delighted to join the cast.”
Day will make his brief debut on screen in the week begining October 18, ahead of a shocking return later in the year.
Speaking of Day's casting, Hollyoaks series producer Paul Marquess said: "Danny Houston is a dangerous but very charming character who makes an aggressive impact in his first episodes.
"Darren plays the part brilliantly and I’m delighted that we're able to bring him back later this year," he added.