This study aimed to understand the experiences of adolescents regarding the perceived impact of COVID-19 on their mental health in Catalonia (Spain). A qualitative exploratory methodology was used with a purposive sample of 30 high-school students regarding their experiences of the self-perceived impact of COVID-19 on their mental health. Data were thematically analyzed using Braun and Clarke method. Three main themes emerged from the data: (a) the challenge of living confined, (b) the footprint of COVID-19 on adolescents’ mental health, and (c) school dynamics during the lockdown. The COVID-19 pandemic negatively impacted adolescents’ mental health, and adolescents perceived a lack of emotional support from educational centers. Therefore, incorporating emotional support in educational centers and offering emotional self-management tools to young students should be a priority. School nurses can play an essential role in recognizing and managing emotional needs and being the natural link between educational and primary care centers.