This dissertation was developed in response to a significant rise in stress, anxiety, and depression within the adolescent population during 2019-2021. The research was exploratory in nature to determine the feasibility of utilizing targeted social emotional mobile applications with high school students. A single case study design with changing criterion and mixed methods allowed for a smaller sample size. Data was collected on the frequency and duration of the teens' App usage and compared to their self-reported levels of stress, anxiety, and depression. In addition to the visual analysis typical of single case design, this researcher chose to conduct correlational analyses of stress, anxiety, and depression to App usage and a Paired T-Test to determine if there was a significant difference in levels of stress, anxiety, and depression pre and post intervention. The seven participants each served as their own control to analyze the uniqueness of the individual experience. Results of the study suggested that App usage had a moderate effect on stress, anxiety, and depression with four of the seven participants experiencing a reduction in symptomology. App usage correlated with stress, anxiety, and depression differently for each individual participant with some significant relationships. The qualitative data collected from participants reflected user insight and recommendations for further consideration in study design and App development. Future directions beneficial for research on targeted social emotional App usage with high school students for self-management of stress, anxiety, and depression should be to conduct the study without time constraints, hold the study during different time periods throughout the school year and summer break, and design the study with follow-up data collection. [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.]