The minimum wage official rises to €10.10 per hour from today.
It is an increase of 30 cent.
The increase has come from a recommendation of the Low Pay Commission which was made in October last year.
It was postponed because of uncertainty with Brexit.
It now means that Ireland has the third-highest rate for the minimum wage across the European Union.
However, Sven Spollen-Behrens, Director of the Small Firms Association, said he does not think it is a good idea.
"Our small business owner/managers are facing difficult times," he said.
"Whilst the economy is still doing well, whilst we are at full employment, our business sentiment of small businesses has gone down substantially and there are two reasons for that.
"Brexit, and the cost burden on small businesses has really increased over the last 24 months substantially."