The service - with music from the Merbecke Choir - will last for about 50 minutes and be followed by the lighting of the Cathedral's Christmas tree and carols around the tree accompanied by the Dixie Ticklers.
Mulled wine and mince pies will be served at the back of the Cathedral.
The service will launch Better Bankside's appeal 'Bring a Better Christmas'. You will also have an opportunity to buy Christmas cards produced by Paintings in Hospitals following a joint schools art project with Better Bankside.
This year the service will be attended by St Nicholas in person, or at least in the form of Canon Jim Rosenthal.