The robbery in the 1800 block of Sweetwater Road was reported at 1:53 a.m., according to National City police.
The victims, all Pizza Hut employees, were approached by a red Ford Mustang or Mitsubishi coupe occupied by four to five people. Police said a man in the front passenger seat spoke to the victims, asking them where they were from before threatening them with a semi-automatic pistol as he demanded their wallets and cell phones.
The victims complied and the gunman and his accomplices fled east on Sweetwater Road in the red car, police said.
A short time earlier, a similar robbery was reported in the 600 block of Palomar Street and police said they were investigating whether the two cases were related.