Growth in the country's services activity improved slightly in June as employment in the sector expanded at its fastest pace this year, leading to a rise in salaries.
Investec's Services Purchasing Managers' Index (PMI) rose to 59.5 from 59.3 in May.
The index has remained above the 50 mark that separates growth from contraction since August 2012.
With unemployment in the European Union's fastest-growing economy dropping rapidly, to 5.1% in June, the sub-index measuring services jobs rose to 57.5 from 56.4 a month earlier.
Respondents said that was partly behind a similarly sharp rise in input costs with salaries identified alongside higher energy and insurance prices as pushing up their cost bases.
"Regardless, the profitability index was little changed in the three months to end-June, with the sequence of above-50 readings now stretching to 20 survey periods," Investec Ireland's chief economist Philip O'Sullivan said.
"It is clear that Irish services companies are upbeat on the prospects for the sector. Given the positive international backdrop, we share this optimism," he said.
A survey published on Monday showed manufacturing growth also hit a five-month high in June.
This was in contrast to growth across the euro zone, which slipped for a sixth successive month to an 18-month low amid concerns about the imposition of trade barriers.