The month's gains were better than April, when ADP said 113,000 private-sector jobs were added, a downwardly revised figure from the 119,000 estimate released last month.
ADP said small businesses were responsible for 58,000 new jobs in May, including 37,000 at companies with fewer than 20 employees and 21,000 at companies with 20 to 49 employees.
Medium-sized firms added 39,000 jobs in the month, and that figure was matched by firms with 500 or more employees, which are considered large businesses.
Among larger businesses, it was the behemoths, those with more than 1,000 employees, that did the bulk of the hiring, adding 33,000 jobs while firms with 500 to 999 employees added 6,000 jobs in the month.
Broken down by industry, construction added 5,000 jobs and manufacturing lost 6,000 in the month. The category of trade, transportation, utilities added 31,000 workers in the month while financial jobs rose by 7,000 and professional service jobs rose by 42,000.
Service-oriented companies added 138,000 jobs, which means goods-producing jobs shrank by 3,000. Many will view that as a sign of a faltering economic recovery.
The report is released two days prior to the Labor Department's monthly Employment Situation report that is taken more seriously by economists and investors. The government's report also is more complete as it includes public and private sector jobs.