Background: Smartphones are integral to modern life, especially among young adults, offering numerous benefits but also raising concerns about their impact on mental well-being and sleep patterns. This study examines how daily smartphone use affects these aspects, focusing on usage patterns, mental health, and sleep quality.Methods: A quantitative study was conducted with 250 young adults aged 18–30 years. Data on smartphone use, mental well-being, and sleep patterns were collected via a self-administered questionnaire. Mental health was assessed using the Depression, Anxiety, and Stress Scale (DASS-21), and sleep quality was measured with the Pittsburgh Sleep Quality Index (PSQI). Correlation and regression analyses were performed to identify relationships and predictors.Results: Excessive smartphone use (>7 hours/day) was strongly associated with higher levels of depression (r = 0.62), anxiety (r = 0.58), and stress (r = 0.53). Pre-sleep smartphone use was significantly correlated with poor sleep quality (r = 0.68) and reduced sleep duration (r = -0.55). Social media was the most time-consuming activity, linked to negative mental health outcomes. Regression analysis showed that smartphone use patterns accounted for 48% of the variance in mental well-being and 55% in sleep quality (p < 0.01).Conclusion: It is concluded that balanced smartphone use is crucial to preserving mental well-being and sleep quality among young adults. Promoting mindful habits can maximize benefits while minimizing risks associated with excessive use. Further research is needed to explore long-term impacts and intervention effectiveness.