A team of vets was called in to sedate the horse before it could be lifted out of the river and up concrete steps using a digger.
One of the animal's hind legs was injured in the fall and the horse was taken away for treatment in a horse ambulance.
Adrian Moore, of Hereford and Worcester Fire Service, said: "The horse was knee-deep in water but the concrete steps from the racecourse to the riverbank are quite steep, so it was trapped.
"We had to sedate it before it could be lifted out of the River Severn, but we believe he will be okay.
"It's not normal for race horses to tumble into the river from the race course. The last time we attended a similar incident was in 1990."
