Project Summary Social anxiety disorder is the most common anxiety disorder in the United States and is particularly common among adolescents. Social anxiety is linked to a host of maladaptive developmental outcomes for youth, including loneliness, other anxiety disorders, and depression, and youth with social anxiety often do not access mental health services. One area of high clinical and practical value is identifying innovative ways to support adaptive coping strategies that will help adolescents manage social anxiety. Dog companionship has the potential to be an effective strategy for supporting youth with anxiety by promoting behavioral and cognitive strategies that are associated with adaptive coping. However, the existing body of evidence regarding pets and mental health suggests that pet ownership is neither universally beneficial in all circumstances, nor applicable to all youth due to the unique and variable nature of dog-youth relationships. Currently, there are significant gaps in the existing evidence regarding specificity in how, for which individuals, experiencing what circumstances, via what processes dog relationships can promote adaptive coping for adolescents. These gaps in nuanced data limit current translational impact and the ability to design and scale interventions. Our overall objective is to harness the potential of dog-youth interaction by identifying the specific ways that these relationships can be optimized to support adaptive coping for adolescents experiencing social anxiety. To address this objective, we will use a multi-method, integrated approach to determine: (Aim 1) longitudinal inter- individual differences in trajectories of associations between dog-adolescent relationships and adaptive coping with social anxiety, (Aim 2) family-level processes involved in adolescent-dog relationships that support adaptive coping with social anxiety over time, and (Aim 3) how the momentary effects of interactions with a pet dog influence continuously collected peripheral physiology as an indicator of anxious arousal. The long-term goal of this research is to decrease the mental health burden of social anxiety during a crucial period of adolescent social development via dog companionship. By identifying both the processes and mechanisms involved in dog interaction and adaptive coping, we will advance practitioners’ ability to maximize adaptive coping strategies supported by dog interactions during a crucial period of adolescent social development. The results will further enable evidence-based recommendations for successfully leveraging dog relationships to inform future research on clinical interventions involving dogs.