Irish people work 90 hours more per year than the EU average.
The longer working hours is one of the key findings in a new report from the Dublin-based EU agency Eurofound.
The study also found that Irish workers, on average, only get 20 days holidays each year compared to 25.7 days for citizens of the first 15 EU member states.
The newer member states tend to have longer working weeks than the older ones.
Ruth Deasy of the EU Commission said the figures showed the Irish were among the most industrious in the European Union.
"Ireland is an outlier," she said. "We're above average for the EU as a whole and 120 hours more per year than the average for the 15 older member states."