The bank's monthly business index had turned positive in February for the first time since the summer of 2012, and in March it was "little changed," dropping from 10 to 9.2, the Fed said.
Numbers above zero indicate growth in business activity.
The new-orders index, also positive for two consecutive months, dropped to 8.2, down five points. The shipments index also fell five points, sliding to 7.8, "a sign that shipments rose at a slower pace this month," the Fed said.
For the fourth consecutive month, the index measuring the number of employees rose, but the Fed called the new reading, at 3.2, a sign of "sluggish" labor conditions.
The index measuring the number of hours worked was unchanged, the report said.