The 25-year-old, who played popular character John Paul McQueen for two years, will appear as Eli, a narcoleptic whose condition causes him to spontaneously fall asleep.
Eli's close friend Jenna (Pippa Duffy) asks him to watch her cat while she's at work, but when Eli notices that she's left something behind, he decides to follow her. However, as he waits as the bus stop, he suddenly falls asleep and misses his ride.
Walking along the road later, he is startled by a group of girls who are out on their Christmas party. When they playfully approach him, he crumples into a heap on the ground. Unbeknown to the flirtatious group, Eli also suffers from cataplexy, a disorder which induces sleep attacks and is commonly linked to narcolepsy.
As he continues his journey, he is soon confronted by two yobs on bikes who try to steal his bag, causing him to collapse once again.
Speaking exclusively to Digital Spy, Sutton said of the role: "It was a really interesting part to play and I did some great research, too. Narcolepsy isn't a condition you really hear about, either. Casualty's a great place to work and I had a blast filming."
Series producer Oliver Kent added: "I'm a big fan of Hollyoaks and this was a great opportunity to cast a fantastic actor like James Sutton."
Sutton's episode - entitled 'Doing The Right Thing' - was filmed in mid-September and will transmit on Saturday, December 13 on BBC One.
Sutton quit his Hollyoaks role in June when the McDean storyline reached its natural Sunset Ending conclusion.
He made a brief reappearance when mad man Niall Rafferty attempted to kill the entire McQueen clan by blowing them up in a church.
Earlier this month, it was announced that Sutton's former co-star Guy Burnet is to make a guest appearance in ITV medical drama The Royal.
> Click here to see the first picture of James in his Casualty role