The Costcutter store in Narberth was found guilty by magistrates in Haverfordwest last Thursday of supplying out-of-date food.
The court heard that an officer from Pembrokeshire County Council's food safety and standards team called at the shop following a complaint, and found nine out-of-date items.
They included some yoghurts which were 22 days past their 'use by date'.
Jack Williams, trading as Costcutter, at High Street, Narberth, admitted the offence and was fined £250 with £100 costs.
Magistrates were told that two warning letters from the council had previously been sent to the store.
Pembrokeshire County Council's public relations officer, Len Mullins, said that all food businesses had a duty to check that no foods were supplied past their 'use by date'.
"Foods marked with a 'use-by-date' are highly perishable and are therefore likely, after a short period, to constitute an immediate danger to human health," he added.