It happened at the Red Lobster on 15-501 just before 10 p.m. Sunday.
Police say customers and staff were inside the store at the time, but no one was hurt. The suspects took money from the business.
Police have not provided suspect descriptions but say they are looking for three men.
The Red Lobster is the same restaurant where a man was shot and killed in the parking lot on August 10. That case remains unsolved.
If you have information about Sunday's robbery, call Investigator Anthony at 560-4583, ext. 29356 or CrimeStoppers at 683-1200. CrimeStoppers pays cash rewards for information leading to arrests in felony cases and callers never have to identify themselves.