Economists had forecast an additional 175,000 jobs would be created in the month to follow the February to March report that has now been revised to show a gain of 201,000 jobs, a downward revision from 209,000.
ADP said businesses with fewer than 50 employees added 58,000 jobs in the month, while companies with 51 to 499 employees added 57,000 jobs.
After two months of modest gains, hiring at firms with 499 or more workers was all but stalled, as large firms added only 4,000 jobs in the month.
Large firms had put together two months with at least 20,000 jobs added to the economy before dropping back to expansion best described as paltry.
Overall, the report, which is issued two days before the monthly U.S. Labor Department report, will disappoint investors.
Coming on the heels of four months with at least 200,000 private-sector jobs gained, the recent report says goods-producing firms lost 4,000 jobs in the month, while service jobs added 123,000 jobs.
Manufacturing lost 5,000 jobs, ADP said.
The figures point to gains that were focused on seasonal, service-sector jobs, such as spring or summer landscaping, recreation and hospitality industry jobs, as opposed to higher-paying jobs in management or finance.