Idaho State University enrollment was 13,845 this fall, down from 14,209 in fall 2012.
ISU joined Boise State University and the University of Idaho in reporting decreases this school year.
Boise State enrollment declined 3 percent and the University of Idaho dropped 5 percent.
ISU officials say a 2 percent drop in the numbers of Idaho high school graduates last spring is partly to blame.
An improving economy has also meant more students are returning to the workforce, which may have also contributed to the decrease, officials said.
ISU enrollment has been flat in recent years.