Abstract: Child solitary and collaborative mother–child play with 21 children with Down syndrome and 33 mental-age-matched typically developing children were compared. In solitary play, children with Down syndrome showed less exploratory but similar symbolic play compared to typically developing children. From solitary to collaborative play, children with Down syndrome increased their exploratory play, attaining the same level as typically developing children. Pretense significantly increased from solitary to collaborative play only in typically developing children. Differences between mothers' play in the two groups mirrored those between their children. Both groups showed similar attunement and synchrony. Mothers contribute to the play development of children with Down syndrome through their own adaptation to their children's limitations and potentialities.