This longitudinal study investigated parents' different pretend play behaviors (substitution, animation, and role enactment) to their infants during free play and the bidirectional links with infants' vocabulary development at 14 months (Time-1: N = 34, M[subscript age] = 14.23 months) and 20 months (Time-2: N = 34, M[subscript age] = 20.33 months), assessed by parental reports. Parents mostly engaged in animation and less frequently engaged in substitution and role enactment during play at both time points. At 14 months, parents' animation input concurrently contributed to infants' receptive vocabulary knowledge beyond parents' overall language input. This relation did not hold for parents' substitution and role enactment. Furthermore, parents' earlier animation input at 14 months negatively predicted infants' expressive vocabulary knowledge at 20 months, and infants' earlier expressive vocabulary knowledge at 14 months negatively predicted parents' animation input at 20 months. These findings suggest that parents might scaffold their infants' vocabulary development through their pretend behaviors. However, only certain pretend behaviors contribute to vocabulary development, possibly due to the differential social and cognitive processes of different pretense forms. We discuss these potential underlying mechanisms and how parents might be sensitive to their infants' vocabulary knowledge when shaping their pretense.