The actor will play nurse Simon Marshall and make his debut in May.
His character will appear in the show “for a few months”.
Quick-witted Marshall, used to dealing with doctors and their egos, is definitely not afraid of standing up to his superiors and undermining hospital hierarchy with his humour.
Announcing Nicholls’ casting, Executive Producer Johnathan Young said: “I can’t give too much away at the moment, but his character is definitely going to have an impact and ruffle a few feathers.”
Nicholls said: “I’m delighted to be joining as a guest on Holby City, it’s a programme I’ve always admired and I’m thrilled to be part of this particular storyline.
“Simon is a confident guy and is sure to be in his element, I can’t wait to get stuck in.”
Follow us on Twitter for more news and updates.