Nearly £13,000 of new fines were given to people at a Plymouth house party hours after they came into force.
Sixteen fines of £800 were handed out on Saturday morning by Devon and Cornwall Police.
The increased fines for illegal indoor gatherings of more than 15 people in England came into effect on Friday as part of stricter Covid-19 regulations.
Sgt Dan Brenchley said the party was an example of a “small minority” who were “continually flouting” lockdown rules.
The new fines will double with every repeat offence, up to a maximum of £6,400.
The penalty for attending illegal indoor gatherings of 15 or fewer people remains £200, while fines of up to £10,000 for holding large illegal gatherings of over 30 people still only apply to the organisers.
Insp Paul Laity tweeted that officers had dealt with 10 other breaches of coronavirus rules on Friday night, mainly involving house parties, and had also made two arrests for drug and weapons offences.
Sgt Brenchley said the new regulations came into effect from 17:00 GMT on Friday, with the £12,800 of fines issued to party-goers in the early hours of Saturday.
“Whether or not the individuals learn from it, or if they pay for it, we don’t know,” he said.
“But we just hope that the more fines increase and the more powers the police get, the more this small minority of people will listen to what the government are saying and help fight this virus.”