Background <p>In the fast-paced modern life, sleep quality has become a key indicator for measuring individual health and quality of life. The mechanisms by which physical exercise influences sleep quality through psychological and behavioral pathways, particularly via smartphone dependence, remain underexplored.</p> Objective <p>To investigate the mediating roles of mobile phone dependence and sleep duration in the relationship between physical exercise and sleep quality, using a chain mediation model.</p> Methods <p>A questionnaire survey was conducted on 1905 college students, and data were processed using Pearson correlation analysis and structural equation modeling.</p> Results <p>Mobile phone dependence significantly mediated the relationship between physical exercise and sleep quality, with an effect size of 0.036 (<i>p</i> &lt; 0.05), accounting for 27% of the total effect. Additionally, mobile phone dependence and sleep duration jointly mediated the relationship, with an effect size of 0.013 (<i>p</i> &lt; 0.05), accounting for 10% of the total effect.</p> Conclusion <p>Physical exercise not only directly improves sleep quality but also indirectly promotes the improvement of sleep quality by reducing mobile phone dependence and increasing sleep duration. This study innovatively identifies a chain mediation mechanism, offering empirical support for designing integrated interventions targeting both behavioral addiction and sleep physiology in college populations.</p>