Background <p>With the rapid development of the internet, smartphones have become an indispensable part of our lives. However, prolonged, excessive and uncontrolled use may lead to the hidden danger of smartphone addiction, posing a threat to users’ physical and mental health. Previous studies have shown that social support may be a factor in alleviating smartphone addiction. However, its specific mechanism needs further exploration. The purpose of this study is to examine the chain mediating effects of negative emotions and self-control on the relationship between social support and smartphone addiction.</p> Methods <p>A cross-sectional survey was conducted from January 2022 to April 2023 in Sichuan Province, China, with 5,188 respondents aged 15 years or older. Spearman’s correlation analysis was used to determine correlations between social support, negative emotions, self-control, and smartphone addiction. We construct a Structural Equation Model (SEM) to explore the pathways of smartphone addiction across different age groups.</p> Results <p>Social support, negative emotions, self-control, and smartphone addiction were found to be significantly related (<i>p</i> &lt; 0.01).In the population aged 15–44, a complete SEM pathway analysis was achieved, while for the population aged 45–64, a simplified version of the pathway analysis was obtained. Among the population aged 65 and above, multiple pathways were found to be nonsignificant. For the full sample, social support not only exhibited a negative correlation with smartphone addiction (β = -0.410; 95% CI: -0.534 to -0.320) but also influenced smartphone addiction through three specific pathways: via negative emotions (β = -0.041; 95% CI: -0.066 to -0.021), via self-control (β = -0.087; 95% CI: -0.119 to -0.063), and via a sequential effect of negative emotions and self-control (β = -0.047; 95% CI: -0.062 to -0.036). The 15–44 age group demonstrated similar pathways to the full sample, whereas the 45–64 age group lost the pathway mediated solely by negative emotions.</p> Conclusions <p>Our study shows that high social support reduces smartphone addiction by diminishing negative emotions and improving self-control.The effect is more pronounced in the 15–44 age group.We suggest strengthening the social support system through more activities and urge relevant departments to improve the mental health education, enhance self-control training, and promote mental well-being to help avoid smartphone addiction.</p> Trial registration <p>Clinical trial number: not applicable.</p>