The six-part drama will serve as a prequel to Spartacus: Blood and Sand and will star Dustin Clare as the gladiator Gannicus.
Zap2It reports that Morrison, who previously played Jango Fett in the Star Wars prequel films, will appear as Doctore, trainer of the gladiators.
Actor Jeffrey Thomas has also been cast as the father of Batiatus (John Hannah).
The pair join Clare, Jaime Murray and Marisa Ramirez in the series. Spartacus: Blood and Sand stars Hannah, Lucy Lawless, Peter Mensah and Manu Bennett will also feature.
Spartacus: Gods of the Arena will air on Starz early next year.