During early childhood, play develops through levels of sensory exploration and manipulation, to functional activities and during the second year of life to the level of pretend and symbolic play. However, little is known about the factors contributing to individual variations in the development of play. The present study investigated associations between maternal sensitivity and play conditions with different ways of engaging and participating and children's development of pretend play. Participants were 64 primiparous mothers and their 30-months-old children. Sensitivity was assessed using the Coding Interactive Behavior (CIB) coding system, and children's play was coded using the 12 Step Play Scale. Analyses showed no significant associations between sensitivity and children's play development but a play condition introducing a story stem was associated with a higher developmental play level and longer duration of pretend play compared to free interactive play. The findings suggest that the use of a story stem may promote pretend play in interactive settings with the mother.