Two air ambulances - the Great North Air Ambulance and the Yorkshire Air Ambulance - attended the scene in remote countryside near Pickering this afternoon.
A Great North Air Ambulance spokesman said the 65-year-old man is thought to have lost consciousness following the fall, though he came round on his way to hospital.
It is not known how serious his condition is.
"The metal footbridge had totally collapsed into the river.
By the time we got there, both men had been retrieved from the water.
We think they were on a shooting party."
It is not known if they were on a shoot at the time of the incident, which took place at around 2.30pm, according to North Yorkshire Police.
North Yorkshire County Council said it was trying to find out who owned the bridge and its current condition.
Two ambulances, a rapid response vehicle and a clinical supervisor from Yorkshire Ambulance Service and two air ambulances from Yorkshire Air Ambulance and Great North Air Ambulance were dispatched to the scene."
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The road was closed in both directions after the crash, which involved an HGV and transit van.