The actor and comedian will play a petty criminal named Michael Rogers, and while exact storylines are being kept secret, it has been revealed the character will find himself caught up in the lives of a family on the Street after breaking into their house.
Speaking about his new role, Dennis said: "I am so thrilled to be joining the cast of Coronation Street; it has always been my favourite television programme, mixing high drama with some of the best comedy on screen.
"I've loved it since the beginning. I grew up watching all the amazing characters in the show.
"I now not only have the chance of meeting them, but also working with them. It doesn't get better than that."
Coronation Street producer Stuart Blackburn added: "Les is a fantastic performer and a real coup for Corrie. I can't wait for him to join the team."
Best known for previously presenting game show Family Fortunes, Dennis is currently appearing in a stage version of the best-selling crime novel The Perfect Murder.
He will start filming on Coronation Street from Monday 27 January and will appear on screen in late March.