The Metro Access bus was northbound near 200th Street about 8:40 a.m. when the man got upset and leapt from the bus, tumbling onto the freeway shoulder.
The driver began trying to get to the side of the road when the man became agitated, but the bus was still going about 35 mph when he jumped, according to officials.
The man, who is in his 40s, was taken to Harborview Medical Center with a broken pelvis, cuts and other injuries.
Officials said the man may have been suffering from a mental illness prior to jumping from the bus.
No one else was hurt, but the Metro driver was described as being very upset over the incident.