Smartphones are found to be a distraction, interfering with parent-child interaction. Our goal was to develop interactive apps for smartphones that would encourage rich conversations between parents and young children. We provided 76 mid- to lower-income families in the Northeastern US with three apps that we developed in collaboration with FableVision Studios and recorded the parent-child dyads interacting with the apps for five-minutes each when they first received them, and again three weeks later, keeping track of app use in-between. Half of the families received the apps-only (N = 38) and the other half received the apps+info in the form of short videos about ways to promote their children’s language development (N = 38). Results of this within-subjects study suggest the apps elicited rich conversations between parents and their 3–4-year-olds. Most of the parent and child language measures increased over time reflecting more sophisticated conversations on our follow-up visit than our initial visit. The significant positive increase from the first visit to the latter visit in children’s language complexity (p < .001), measured as mean length of utterance, was associated with how frequently the family used the apps in between visits. There was no main effect of group, yet within the apps+info group, there was a positive association between the number of informative videos watched and parents’ vocabulary use and conversations at visit 2, controlling for those speech measures at visit 1. The results suggest that interactive apps can help transform smartphones into opportunities for parent-child conversations and learning.