This paper aims to study the role of the social robot Probo in providing assistance to a therapist for robot assisted therapy (RAT) with autistic children. Children with autism have difficulties with social interaction and several studies indicate that they show preference toward interaction with objects, such as computers and robots, rather than with humans. In 1991, Carol Gray developed Social Stories, an intervention tool aimed to increase children's social skills. Social stories are short scenarios written or tailored for autistic individuals to help them understand and behave appropriately in social situations. This study shows that, in specific situations, the social performance of autistic children improves when using the robot Probo, as a medium for social story telling, than when a human reader tells the stories. The robot tells Social Stories to teach ASD children how to react in situations like saying “hello“, saying “thank you“ and “sharing toys“. The robot has the capability of expressing emotions and attention via its facial expressions and its gaze. The paper discusses the use of Probo as an added-value therapeutic tool for social story telling and presents the first experimental results. Keywords: social robot; ASD children; social story; robot assisted therapy