Seattle Fire Department spokesman Kyle Moore says the man was unable to communicate when medics were called to the scene at 3:17 a.m. Tuesday.
He was taken to Harborview Medical Center in Seattle with life-threatening injuries from multiple broken bones.
Moore says University of Washington police were asked to investigate because the man is believed to be a student.
It's unknown how long he was in the alley before he was found by his friends. There were no witnesses to the fall, but a third-story window was open.