Crews were alerted to the fire at Monsoon Indian restaurant in Goring Road at just before 2.30am.
Three fire engines from Worthing Fire Station were sent to the scene.
A spokesman for West Sussex Fire & Rescue Service said: “Upon arrival crews were faced with a fire involving a kitchen on the ground floor of the property, and firefighters wearing breathing apparatus quickly brought the fire under control using two hose reels and a jet.
“Firefighters remained on scene turning over and damping down, and used a thermal imaging camera to ensure there were no further hotspots.
“Fortunately there were no casualties as a result of this fire, which is believed to have begun accidentally.
“The last crew left the scene at 5.43am.”
Residents living in the flats above the restaurant were evacuated from their homes.
See more pictures here: Residents evacuated after fire at Worthing restaurant – in pictures