Improving breastfeeding rates is a global goal. To achieve it, actions targeting modifiable factors that influence the breastfeeding experience, such as maternal self-efficacy, could be a promising path, especially with preterm infants' mothers. Considering the current ubiquitous technology, we developed a mobile application for mothers of preterm infants to constitute a breastfeeding information and support platform. The study was developed in three phases: a survey to determine characteristics and preferences of preterm infants' mothers; the app development by an interdisciplinary team, following the principles of Disciplined Agile Delivery; and the face and content validation by 10 professionals. The app contains 80 screens and 11 strategies to address prematurity, lactation, breastfeeding, peer support, maternal emotions, resilience, and motivation. Nurses can apply their expertise by designing mHealth-based interventions, employing scientific evidence, and considering the interests and preferences of the target population. Future studies will assess the user experience, the effect on breastfeeding self-efficacy, and breastfeeding rates, and develop a culturally adapted English version of the app for women in Canada.