Firefighters from Bracknell and Wokingham were called to the junction between Jigs Lane North and Forest Road at about 2pm.
They said two of the cars, a Volkswagen Polo and a Ford Focus, had been involved in a head-on collision and then a third car, a Vauxhall Astra, collided with the vehicles.
Fire crews had to cut off the roof of the Astra to allow paramedics to remove the woman from the car on a backboard.
She was complaining of neck and spinal injuries and was taken to Royal Berkshire Hospital for further treatment.
Police closed the road for about an hour and a half, with emergency services leaving the scene at about 3.30pm.