Adolescents and young adults are most at risk for developing problematic smartphone and social media use that negatively impacts their mental health and well-being. Students' perceptions of their school environment are likely a key area of potential risk and protective factors for adolescents' problematic smartphone and social media use, but more scientific evidence is needed. To examine the associations between school climate, connectedness, affective engagement, and problematic smartphone and social media use, 529 Italian high school students were surveyed. Statistical methods (Pearson correlation coefficient and multiple regression analysis) were used to analyze the data. The results of the study showed that all variables in the study were significantly correlated with each other. There was a negative correlation between school climate, connectedness to school, affective school engagement, and problematic smartphone and social media use. Among the predictor variables, school climate and connectedness to school were the only predictors of both problematic smartphone and social media use. Studies using an experimental design should be conducted to confirm our findings and demonstrate directionality. Mobile media education in school, combined with adolescents' sense of well-being at school, could play an important role in preventing problematic smartphone and social media use.