The replacement market hall should be ready this time next year
Rent is to be scrapped for more than 100 traders at Carmarthen market until they move into a new hall next year.
It is one of a package of measures to help keep them in business while work continues on the £50m redevelopment of the town centre.
They have been hit by the closure of a nearby carpark and traders claim hoardings around the current market hall give the impression it is shut.
New "market open" signs will be put up and an advertising campaign launched.
The package of measures was agreed by Carmarthenshire council's executive board ahead of a meeting with the traders later on Monday.
A total of 16 shops and 86 stallholders will now enjoy free rent.
Work finally started on the £50m redevelopment of the old cattle mart site last month following years of delays.
It will include a new market hall, department store, smaller shops and restaurants and multi-screen cinema.
Council chief executive Mark James said: "We are now at an exciting stage of getting things built."
But he added: "There is no doubt it is difficult trading conditions for traders.
"The new market is fully let and should be open by this time next year - we hope to keep them trading in the existing market until then."
The redevelopment of the old cattle mart site has resulted in the loss of around 1,500 car parking spaces although a new park and ride is operating out of the showground at Nantyci.
Scrapping rents, which will cost the council £200,000 in income, was put forward by the Independent and Labour ruling coalition.
A spokesman for the main opposition Plaid Cymru group said: "It's good news because at present in the centre of town and especially around the market area are having quite a difficult time of it."
Market trader Liz Bellamy said they had been trying hard to get the message across they were still open for business.
She said in particular many visitors from outside the town were under the impression the market had closed.
"I think they [Carmarthenshire Council] are appreciating just how difficult it is for us," she added.
"We are still here and still open for business and we need people to come and visit and support us."