U.S. private-sector employers added 178,000 jobs in May, fewer than Econoday's consensus estimate of 187,000 jobs, according to data from the ADP National Employment Report.
The total number of jobs added in April was revised down to 163,000 from 204,000.
"Job growth is strong, but slowing, as businesses are unable to fill a record number of open positions," said Mark Zandi, chief economist of Moody's Analytics.
"Wage growth is accelerating in response, most notably for young, new entrants and those changing jobs. Finding workers is increasingly becoming businesses' number one problem," Zandi added.
The services sector added 114,000 jobs in May, while employment in the goods-producing sector rose by 64,000.
Within the service sector, professional and business services led the gains, adding 61,000 jobs. Administrative and support services, and education and health services each added 35,000 jobs. Employment in leisure and hospitality rose by 33,000 jobs, while that in healthcare and social assistance increased by 26,000 jobs. Employment in trade, transportation and utilities declined by 23,000 jobs.
Within the goods-producing sector, the construction industry added 39,000 jobs, manufacturing gained 14,000, and natural resources and mining added 11,000.
Employment at medium-sized businesses rose by 84,000 jobs. Large businesses added 56,000, while small businesses reported job gains of 38,000.

