The sector continued adding jobs, although at a slower pace, with hiring falling to 53.3 from 57.2.
A separate report on Wednesday showed that the services sector made up the bulk of the job creation in March, with 151,000 jobs added last month out of the total 158,000.
The Labor Department is set to release its measure of private and public job creation on Friday, and estimates are that about 175,000 total jobs were added last month, with the unemployment rate possibly ticking up from a four-year low to 7.8 percent.
Most of the ISM's survey's respondents were positive about current conditions, with several seeing increases in spending by consumers, which is expected to help on the hiring front.
Consumer spending has been increasing even though workers are seeing less money in their paychecks because of a recent increase in payroll taxes.