Objective <p>Metacognitive theory suggests that maladaptive beliefs about thinking are associated with the cognitive attentional syndrome (CAS), which is characterized by repetitive negative thinking and heightened threat monitoring. This study examined a dual-mediation model in which rumination and anxiety sensitivity were tested simultaneously as mediators of the relationship between metacognitive beliefs and sleep quality in a nonclinical sample.</p> Methods <p>A total of 346 Iranian adults (18–60 years) completed validated self-report measures of metacognitive beliefs, rumination, anxiety sensitivity, and sleep quality. Structural equation modeling (SEM) with bias-corrected bootstrapping (2,000 resamples) was used to test the hypothesized model.</p> Results <p>The model demonstrated acceptable fit to the data (CFI = 0.96, RMSEA = 0.074). Metacognitive beliefs were not significantly associated with sleep quality after including the mediators. However, significant indirect effects were observed through rumination (β = 0.32, 95% CI [0.20, 0.40]) and anxiety sensitivity (β = 0.28, 95% CI [0.17, 0.37]). The model explained 50% of the variance in sleep quality.</p> Conclusions <p>The findings indicate that metacognitive beliefs are statistically associated with poorer sleep quality indirectly through rumination and anxiety sensitivity in a community sample. These results support the value of examining transdiagnostic cognitive–emotional processes in sleep research. Due to the cross-sectional design and reliance on self-report measures, causal inferences cannot be drawn. Future longitudinal and experimental studies are needed to clarify the temporal relationships and clinical utility of these pathways.</p>