The October 2021 declaration of a national emergency for child and adolescent mental health resulted in the call for innovative methods for addressing barriers to seeking care, including the suggestion of mental health apps using transdiagnostic approaches. In line with this, the current study sought to validate the app "Amaru: The Self-Care Virtual Pet" with adolescents. Amaru, created by a psychologist, uses the storyline of helping an anxious winged cat to assist players in creating self-care habits by employing positive psychology interventions (e.g., mindfulness, journaling, affirmations). The study included two parts: a case study of an adolescent recruited from a rural community in Western PA and a sample of 18-year-olds recruited from a university subject pool. All participants were asked to play the game for eight weeks, setting self-care goals of mindful meditation, journaling, and a goal of their choice. Measures of anxiety, depression, inattention, psychosocial functioning, mindfulness, and emotion regulation were completed at baseline, week four, and week eight, and participants provided feedback on their engagement with the app during the last survey. The case study showed improvements across all measures, while the subject pool sample only showed significant reductions in inattention and significant increases in mindfulness. However, participants who used Amaru daily demonstrated significant decreases in emotion dysregulation. Participants indicated Amaru was enjoyable and easy to use. The current study provides initial support for using Amaru to assist with the development of self-care skills in adolescents. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]