This study assessed the effects of maternal smartphone use on mother-child interaction. Thirty-three Israeli mothers and their 24-to 36-month-old toddlers (16 boys) from middle-high socioeconomic status participated in three within-subjects experimental conditions: maternal smartphone use, maternal magazine reading, and uninterrupted dyadic free-play. The mothers produced fewer utterances, provided fewer responses to child bids, missed child bids more often, and exchanged fewer conversational turns with their children when engaged with a smartphone or printed magazines compared to uninterrupted free-play. The quality of maternal responsiveness was also decreased. These findings suggest maternal smartphone use compromises mother-child interaction, which given smartphone ubiquity in daily life may have negative effects on child development in various domains, including language, cognition, and socioemotional regulation.