Background <p>Excessive smartphone use has become increasingly prevalent among young adults, contributing to sedentary behavior, sleep disturbances, and physiological dysfunctions. However, the interrelationship between screen time, musculoskeletal health, sleep quality, and cardiovascular parameters remains inadequately explored.</p> Objective <p>To determine the association of daily smartphone screen time with sleep quality, musculoskeletal health, and cardiovascular function among young adults.</p> Methods <p>A cross-sectional study was conducted among 75 participants (aged 18–30&#xa0;years) recruited from a university setting. Average daily screen time was objectively recorded over four consecutive weeks. Sleep quality (Pittsburgh Sleep Quality Index), musculoskeletal health (Musculoskeletal Health Questionnaire), and cardiovascular indices (systolic/diastolic blood pressure, resting heart rate, VO₂max via 20&#xa0;m Beep Test) were assessed. Correlation analyses were performed using Pearson’s or Spearman’s coefficients based on normality.</p> Results <p>Mean daily screen time was 405.3 ± 123.9&#xa0;min. Screen time showed a strong negative correlation with musculoskeletal health (r = –0.66, p &lt; 0.001) and aerobic capacity (ρ = –0.72, p &lt; 0.001), and a strong positive correlation with poor sleep quality (r = 0.60, p &lt; 0.001). Systolic blood pressure correlated moderately with screen time (r = 0.35, p = 0.003), whereas diastolic pressure and resting heart rate showed no significant association.</p> Conclusion <p>Prolonged smartphone screen exposure adversely affects musculoskeletal, sleep, and cardiovascular health in young adults. Findings emphasize the importance of moderated digital use, ergonomic awareness, and regular physical activity to mitigate screen-induced physiological risks.</p>