In spite of the close relationship between gestures and expressive language, little research has examined the roles of the parents' and children's gestures in the development of expressive language abilities in autistic children. Previous findings are also inconclusive. In the present study, we coded the gestures produced by the parents and their autistic children in parent-child interactions and compared the influence of their gestures on the children's expressive language abilities (N = 35; M = 4;10). Autistic children's deictic gestures positively predicted their Mean Length Utterance (MLU), word types, and word tokens whereas parents' deictic gesture inputs negatively predicted MLU and word types. The findings shed light on the importance of the gestures made by autistic children, which may trigger parents' gesture-to-word translation.