Police, ambulance, firefighters and the York Rescue Boat were all called out to Kings Staith at about 11.40pm after reports of someone in the water.
A spokesman for North Yorkshire Fire and Rescue Service said: "Crews from Acomb and York responded to a report of a woman in the river.
"On arrival, crews located a woman in her 20s who had entered the river but had been pulled out onto a stationary canal boat by a member of the public.
"Crews transferred the woman onto the fire service boat to transport her to a location with easier access to the bank side.
"She was left in the care of ambulance crews undergoing an assessment before being transported to hospital for precautionary checks."
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