Recent increase in children's screen activities has raised concerns that screen time may replace face-to-face interaction, and hence impair children's development of emotion understanding. This longitudinal community study of 960 Norwegian 4-year-olds, followed up at ages 6 and 8, examined bidirectional relations between screen use and emotion understanding. Results revealed that more screen time at age 4 predicted lower levels of emotion understanding at age 6. In addition, television in children's bedroom at age 6 forecasted lower levels of emotion understanding at age 8. The effect of TV watching on emotion understanding was gender moderated, with stronger effects of TV watching observed among girls, but no significant effects detected among boys. In contrast, gaming forecasted lower level of emotion understanding in boys, not girls. Results are discussed in the light of the importance of face-to-face interaction to preserve the development of social-emotional competence among young children. Statement of contribution What is already known on this subject? We know that children's screen activities correlate with poorer social competence and with decrease of the quantity and quality of interaction with parents and siblings. The capacity to understand emotions in others is primarily learned through interaction with primary caregivers, but little is known how children's screen use influences development of emotion understanding. What the present study adds? We found that more TV watching among girls at age 4 predicted lower levels of emotion understanding at age 6. Furthermore, TV in child's bedroom at age 6 forecasted lower levels of emotion understanding at age 8.