The volume of retail sales fell by 2.4% during May, according to new data from the Central Statistics Office.
Year on year, however, sales are up 1.1%, the figures show.
Sectors which saw the largest monthly drop in sales volumes included food, beverage and tobacco, which was down 5.3%, and fuel which fell 5.1%.
But sale volumes that recorded the greatest increases include bars, up 4.5%, and electrical goods, up 2.7%.
Excluding vehicle sales, the overall volume of sales was down 1% last month when compared to the previous month.
Annually, the volume is up 3.6% under this measure, the CSO said.
The value of retail sales was 2.3% lower in May compared to April, and up just 0.6% compared to the same month in 2018.
Stockbroker Davy said it still thinks the economy is on track to record a 3% rise in consumer spending this year, with little sign of Irish households reining in spending because of Brexit uncertainties
"Our forecast is for 5% Irish GDP growth in 2019, ahead of most official projections for circa 4% growth," it said in a research note.
"One key difference is that we expect consumer spending to grow by 3% in 2019, a similar pace to 2018."
"Thus far, the retail sales data suggest that we are broadly on track. Another cross-check are government VAT receipts, up 6% in the first five months of 2019 after 7% growth in 2018."
While economist, Alan McQuaid, also said the results were mixed.
"The "core" retail sales figures for the first five months of 2019 suggest that the Irish economy continued to grow at a solid pace in the first half of the year, but growth in the second half of the year is likely to be slower as a result of increased global trade tensions and of course the ongoing uncertainty over the UK's future in the EU, with a "hard Brexit" still a real possibility," he said.
