Children with low executive functions (EFs) are described as having lower levels of playfulness, the quality of children's play, compared to children with EFs within the normal range. However, how playfulness in children with low EFs develops over time remains unclear. Additionally, little is known about how parental playfulness and parental playtime with their child affect these developmental trajectories in children with low EFs. To address these research gaps, we measured playfulness in 62 children with low EFs and 62 children with EFs within the normal range aged 3 to 6 years at three time points over 2 years. We used the Children's Playfulness Scale, which captures multi-informant perspectives from parents and teachers. Moreover, the parents of children with low EFs reported their own playfulness and their playtime with their children at T1. Repeated-measures hierarchical linear models indicated significantly lower levels of playfulness in the children with low EFs than in the controls, with no significant changes observed over 2 years in either group. In the children with low EFs, we found a significant positive relationship between parental playfulness at T1 and children's playfulness 2 years later but a significant negative relationship between parental playtime at T1 and children's playfulness 2 years later. These results prompt a broad discussion on potential implications for the enhancement of playfulness in children with low EFs within the family environment.