Background <p>With the widespread use of smartphones, concerns have emerged regarding their potential impact on mental health and sleep. This study examined the associations between smartphone addiction and symptoms of anxiety, depression, and sleep disorders among university students.</p> Methods <p>A descriptive correlational design was employed with a convenience sample of 460 Egyptian university students from Fayoum University &amp; Ain Shams University. The total sample consisted of (140 males, 320 females) aged 19–24 years. Data were collected using validated Arabic versions of the Smartphone Addiction Scale, GAD-7, the depression subscale of the HSCL-25, and a Sleep Disorders Scale. Pearson correlations and simple linear regression analyses were conducted.</p> Results <p>Smartphone addiction was positively associated with anxiety (<i>r</i> = 0.485), depression (<i>r</i> = 0.627), and sleep disorders (<i>r</i> = 0.567) (<i>p</i> &lt; 0.001). Regression analyses indicated that smartphone addiction accounted for 26%, 23% &amp; 30% of the variance of anxiety, depression, and sleep disorders. These results indicate that smartphone addiction may serve as a potential risk marker for anxiety, depression, and sleep disorders.</p> Conclusion <p>Higher levels of smartphone addiction were significantly associated with increased psychological distress and sleep disturbances. While causal inferences cannot be drawn due to a cross-sectional design, smartphone addiction may function as a potential risk marker within a broader network of psychological vulnerability. These findings highlight the need for longitudinal and multivariate research to better clarify the underlying mechanisms and directional relationships.</p>