Officers raced to the restaurant in East Laith Gate at around 6pm last night following reports of a man causing a disturbance at a restaurant, which has not been named by police.
A spokesman for Doncaster Central Neighbourhood Policing Team said: “He was initially arrested for being drunk and disorderly, but was then found to be in possession of numerous bags of what is believed to be class A drugs.
"Following a search of his home address a Samurai type sword was seized, along with more drugs.”
He is now being investigated for new offensive weapon offences, a South Yorkshire Police spokesman said.
The man remains in police custody and will be interviewed later today.
East Laith Gate is home to a number of restaurants, takeaway shops and bars.