Background: Many adolescent mothers (AMs) are parenting young children under highly stressful conditions as they are managing first-time parenthood, poverty, lack of housing, school/work demands, and challenging peer and familial relationships. Increasing AMs effective emotion regulation strategies using 'just-in-time' mobile technology has the potential to intervene at various points in the emotion regulation process to provide support for more adaptive emotional and behavioral regulation in the course of their daily life. Objective: The goal of this paper is to examine the acceptability, feasibility, use patterns, and mechanisms by which the technology fostered AMs adaptive emotion regulation strategies under real-life conditions. Methods: Participants (N=49) were enrolled in the intervention condition of a randomizedcontrolled pilot study of homeless AMs living in group-based shelters. Intervention activities involved a blended intervention consisting of in-person, provider-delivered intervention sessions and the companion Calm Mom technology. Calm Mom consisted of a mobile app and wrist-worn sensorband for the ambulatory measurement and alerting of increased electrodermal activity (EDA), a physiological measurement of stress. We examined logs of mobile app activity and conducted semi-structured qualitative interviews with a subsample (N= 10) of participants. Qualitative data analysis was guided by the theoretical frames of the intervention and a technology acceptance models and included an analysis of emerging themes and concepts. Results: Participants used one or more elements of the technology on average, 44.11% of days they had the Calm Mom technology (SD = 24.82). Overall, participants indicated that one or more of the elements Calm Mom supported their ability to effectively regulate their emotions in the course of their daily life in ways that were consonant with the intervention's theoretical model. For many AMs, the app became an integral tool for managing stress. Due to technical challenges, fewer participants received sensorband alerts however, those that received alerts reported high levels of acceptability as the technology helped them to identify their emotions and supported them in engaging in more adaptive behaviors during real-life stressful situations with their children, peers, and family members. Conclusions: Calm Mom is a promising technology for providing theoretically driven behavioral intervention strategies during real-life stressful moments among a highly vulnerable population. Future research efforts will involve addressing technology challenges and refining tailoring algorithms for implementation in larger scale studies.