Deputy Akers of the King County Sheriff's Office says it appears the man was under the influence of drugs or alcohol when he tumbled off the bridge at about 5:45 a.m.
The man then used his cell phone to call for help. Firefighters responded, but it took them more than an hour to find the victim, who was lying at the bottom of a ravine with broken bones.
Once the man was located, responders used ladders and ropes to extricate him and pull him out of the ravine. He is expected to recover.
One lane is closed in each direction of Highway 18 during the rescue.