Adults' behaviour in interactions with children is assumed to influence children's playfulness. However, little is known about how the quality of teacher-child interaction in early childhood education and care affects the development of children's playfulness, although the interaction quality has been identified as a strong predictor of children's development in various domains. The present study examined cross-sectional and longitudinal associations between children's multidimensional playfulness and the quality of teacher--child interactions. At first measurement, 62 teachers in early childhood education and care (ECEC) were observed to assess the quality of their interactions with children using the standardized CLASS Toddler scale. The playfulness of 393 children was assessed using the children's playfulness scale at the same time and one year later. No significant effects were found cross-sectionally. Longitudinally, high interaction quality in learning support was marginally negatively related to children's total score of playfulness and significantly negatively to the playfulness dimensions of cognitive and physical spontaneity. We discuss which teaching styles might hamper or promote children's playfulness.