This study investigated the relationship between social media use and mental health, using patients and staff associated with Nsambya Hospital, Kampala, as the case. Social media has become deeply embedded in daily life, and concerns have grown about its psychological effects, especially among young adults. The main objective was to examine the relationship between social media use and mental health outcomes. Three specific objectives guided the study: to establish patterns of social media use; to assess the effect of social media use on anxiety, depression, and self-esteem; and to determine the relationship between intensity of use and mental health outcomes. A cross-sectional correlational design was used with 150 respondents selected through stratified random sampling. Data were collected using standardised scales adapted for the setting and analysed using descriptive statistics, Pearson correlation, and multiple regression. Results showed that heavy and problematic social media use was positively correlated with anxiety (r = 0.54) and depressive symptoms (r = 0.49) and negatively correlated with self-esteem (r = −0.42), all significant at p < 0.01. Regression indicated that intensity of use and problematic use jointly explained 46% of the variance in poor mental health outcomes. The study concluded that social media use is a significant, though not sole, contributor to mental health strain, and recommended digital-wellbeing education and screening in health settings. This article discusses a sensitive topic; readers affected by these issues are encouraged to seek professional support.