Early parenting practices play an important role in shaping children’s future outcomes. In particular, high-quality early interactions can facilitate language learning and school performance. The rise of phone-based parenting applications ("apps") could deliver low-cost interventions on parenting style to a wide variety of populations, especially the parents of very young children, who are often difficult to reach in other ways. Yet little is known about the effects of communicating to parents through app-based interventions. In two studies (one preregistered), we showed parents short videos depicting age-appropriate parent-child activities from a parenting app. We found that after watching the video, parents spoke more and made more bids for joint attention, as compared with controls who watched no video (experiment 1) or a science video (experiment 2). These results suggest that activity videos can lead to positive changes in parent engagement, providing support for the use of such videos in parenting interventions.