Authorities say the victim was assaulted by the man while biking across the bridge just before 7 a.m.
He was knocked off his bicycle by the force of the attack, which was apparently unprovoked.
The suspect was naked by the time responding police arrived on the bridge.
Officers covered the suspect with clothing and took him to Elmhurst Hospital for evaluation. The bicyclist was taken to New York Presbyterian Hospital with a jaw injury.
The ensuing police investigation closed the bridge's lower level for an hour, causing delays for the morning commute.