A house party with 15 people was broken up by police - a day after such events were labelled "totally unacceptable" by a senior officer amid the pandemic.
Gwent Police confirmed all those at the house, in Aberbargoed, Caerphilly county, were given fines on Saturday.
A total of 54 people were fined last weekend for breaching Covid-19 rules, such as holding parties, the police force said.
Level four lockdown rules were imposed on Wales before Christmas.
People are not allowed to mix with others outside their household or "bubble" and all but essential travel is banned.
'Dangerous and selfish'
On Friday, Gwent Police Ch Supt Mark Hobrough confirmed officers were called to house parties in Pontypool, Newport and Rhymney, Caerphilly last weekend.
He said: "Organising parties and gatherings is dangerous, selfish and is totally unacceptable in light of the current threat we face.
"For those who blatantly go against the restrictions, we will take enforcement action.
"Coronavirus levels remain high across much of Gwent, and by following Welsh Government advice we're all saving lives and protecting the NHS."
Fines of £800 for anyone attending a house party of more than 15 people will be introduced in England from next week under new Covid measures.
In Wales, fines for lockdown breaches start at £60 but persistent offenders can be fined up to £1,920.