The actor will play the hotel’s hapless assistant manager Ashley Dodds, who is left in charge over Christmas.
Alexander Armstrong, Pam Ferris and Warren Clarke are also set to appear in the comedy, called Christmas At The Riviera.
It has been written and directed by Mark Bussell and Justin Sbresni, the team responsible for BBC1’s The Worst Week Of My Life.
ITV director of drama Laura Mackie said: ‘The lively and captivating script combines their talent for high comedy with poignant drama and captures all the highs and lows of the festive season.’
Shearsmith is also about to star in a Radio 4 sitcom called Self-Storage, due to start on September 19.
He will play Dave, a divorced man who loses his job and ends up living in a self storage unit.
The show also stars Tom Goodman-Hill, Mark Heap and Susan Earl, and features an appearance by Phil Nichol.
Tom Collinson, who co-wrote the series with Barnaby Power, said: 'At one point I had to move my stuff into a storage unit in East London. It was horrible. A faceless, modern nightmare with rows of pods full of people’s lives.
‘Then I thought “I could live here”..’
