Mobile device use has become ubiquitous with daily life, thus providing opportunities to reach parents to promote healthy eating and physical activity in children. Using a socioecological framework and user-centred design approach, the objective of this study was to understand the context in which parents use their devices and their preferences for a digital programme. The formative research phase of the electronic healthy environments (eHEROs) study used a multiple-methods design, consisting of a quantitative survey (n = 116) and a semi-structured qualitative interview (n = 16). Individual- (i.e. digital literacy) and environment-level (i.e. home internet connection) factors were associated with likelihood to participate and preferences for intervention format. Participants outlined key preferences for mobile app content, including modality (audio and video with text), flow (access), and duration (5–15-min lessons). Motivation for participation related to the relevance of the content, feelings of accomplishment, and creative and engaging packaging. Lastly, participants desired opportunities to build community and connect with other parents, preferably through group meetings. Identifying and incorporating the population’s preferences and requirements into the digital design are needed to optimize adoption, engagement, and retention of intervention use.