West Yorkshire Police say an unlicensed music event was shut down in Keighley over the weekend.
Officers attended the premises on Becks Road, which is in the Oakworth Road area of town, late on Saturday night.
A man was served with a £10,000 fine for breach of coronavirus restrictions, while those present were also given £800 fines each.
Police say a large quantity of alcohol was also seized from a bar.
Chief Inspector Daniel Ware, of Bradford District Police, said: “We would again like to thank the majority of the public of Bradford District for their continued support in these difficult times.
“While restrictions are easing, I would like to remind people we are still in a pandemic and the rules are there to protect the health and safety of the public.
“I would also like to reassure the public that we will take enforcement action against those who put us all at risk by choosing to flagrantly break the rules.”