This is the first time Western has topped the list.
Western ranked second among medium colleges last year.
Local Peace Corps representative Jill MacIntyre Witt says Western students value the experience of volunteering.
She says many Western students also volunteer through service learning programs on campus in Bellingham and internationally.
Western currently has 73 undergraduate alumni serving in the Peace Corps.
A total of 885 Western alumni have served as Peace Corps volunteers since the agency was founded in 1961.
The top Peace Corps colleges in all three categories this year are from Washington State.