American parents describe bonding with their child as a primary reason for engaging in shared picture book reading. One prominent reading intervention (dialogic reading) reliably increases language outcomes, but until recently, has not been evaluated for how well it promotes warm parent-child interactions. In this study, a digital application designed to promote parent-child conversation by modeling dialogic questioning also increased mutuality, positivity, and on-task behaviors. Three-and 4-year-old American children (n = 73) and their parents were randomly assigned to read 10 times at home either: (a) an eBook with a character who modeled dialogic questioning (experimental); (b) a version of the same eBook without modeling (control); or (c) to choose between versions for each reading (choice). An adaption of the PARCHISY coding scheme was used to evaluate parent, child, and dyadic behaviors during in-lab readings at the beginning and end of the 2-week home reading period. At the final visit, experimental group families showed significant growth in mutuality (i.e., responsiveness, reciprocity, and cooperation), on-task behaviors, and parent and child positivity, and displayed more of these behaviors than families not exposed to modeling. Some increases in mutuality and positivity also emerged in families in the choice condition, but fewer than in families who only read the eBook with modeling. Parents and children exhibited no significant changes in negativity in any condition. This study suggests that carefully designed digital technology has the potential to foster positive shared reading interactions between parents and young children.