Problems with adherence are common among adolescents with Type 1 diabetes (T1D), who must follow a complex treatment regimen. Positive psychology interventions increase adherence and improve health outcomes in adults with chronic conditions; however, they have not been translated to pediatric populations. We evaluated the acceptability and feasibility of Check It!, a positive psychology intervention to improve adherence in adolescents with T1D. Adolescents with T1D and their parents were randomized to a positive psychology intervention (via phone or text message) or an attention control (education) group. Exit interviews and satisfaction surveys were conducted with adolescents (n = 63) and parents (n = 55) to assess the acceptability and feasibility of Check it! from a representative sample of each group. Chi-square, t tests, ANOVA, and content analysis methods were used to analyze data. Parents and adolescents indicated interest in the intervention, and enrollment numbers support feasibility. In terms of intervention delivery, we identified challenges in implementing the positive psychology reminders to adolescents, particularly in the phone group. Parents in the positive psychology group appreciated the reminders to provide affirmations to their children, and adolescents enjoyed the affirmations and reported using the positive psychology exercises. Regarding acceptability, participants in both groups reported high satisfaction with the intervention overall. Participants reported favorable experiences with Check It! and findings indicate that text messages are more feasible than phone calls for interventions with adolescents. Overall, a positive psychology intervention delivered with automated text messages is feasible and acceptable to adolescents with T1D and their parents.