New figures from the Central Statistics Office show that the volume of retail sales fell by 2.4% in September due to weaker car, clothing and footwear sales.
However, the volume of retail sales rose by 1.2% in September on a yearly basis - the lowest annual rise so far in 2017.
In the first nine months of the year, sales were 3% higher than in the same period of 2016.
The CSO said that if car sales are excluded, retail sales rose by 1.3% on a monthly basis in September, while they jumped 7.7% on an annual basis.
Today's CSO figures show that car sales dropped 18% in September, while clothing, footwear and textiles sales were down 3.1%.
But September also saw a 4.7% increase in furniture and lighting sales, while electrical goods sales increased by 3.4%.
Meanwhile, the value of retail sales fell by 4.4% in September compared to August, while they were 1.6% lower compared to the same time last year.
Commenting on today's figures, Merrion economist Alan McQuaid said that while retail sales remain erratic on a monthly basis and are still swinging back and forth, the underlying trend is positive.
Mr McQuaid said that while most attention has been on new car sales in the past couple of years, which will be lower in 2017 than 2016, personal spending in other areas has picked up over the same period and is becoming more broad-based.
He said it now now forecasting headline retail sales volume growth of 2.5-3% in 2017, while "core" sales are projected to be 6.5-7% higher in the year.
