The actor will appear as Frank, the brother of Las Vegas Sheriff Ralph Lamb (Dennis Quaid) in the new drama from Goodfellas writer Nicholas Pileggi and Without A Trace producer Greg Walker.
Set in the 1960s, the project tells the true story of Lamb's face-off with Johnny Savino (Michael Chiklis), a Chicago mob fixer with big plans for the city.
The Matrix actress Carrie-Ann Moss is rumoured to be playing Assistant District Attorney Katherine O'Connell.
O'Mara will only commit to the project if a second season of Terra Nova does not go ahead, according to Deadline.
The show was axed by Fox at the beginning of March, but producers are apparently discussing reviving it on Netflix.
After Terra Nova's cancellation, O'Mara thanked fans on Twitter for their "immense outpouring of love & support".