The Irish services sector expanded at the slowest rate since February 2014 in April, the latest Investec purchasing managers' index shows.
However, the report still indicates a sizeable increase in activity in its headline figure of 60.6 - anything over 50 indicates expansion.
March's figure was 60.9.
Investec Ireland chief economist Philip O'Sullivan said the report "reveals strong growth in activity in the sector, albeit at a somewhat slower pace than had been seen in previous months."
Investec's analysis shows levels of optimism are at a 14-month high amid indications that improving economic conditions are translating to increases in new projects.
"Services companies based in Ireland reported higher new business from both domestic and overseas clients," Mr O'Sullivan said.
"Given the continued rise in incoming new business, it is no surprise to see that firms continue to add to headcounts," he added.