Background and objectives: The interest in studying the relationship between bruxism and sleep apnea has increased over the past decade, given its prevalence and its implications for both oral and overall health. Bruxism occurs in a significant portion of the population, with an overall incidence ranging between 8 and 31%. Obstructive sleep apnea affects 4–6% of middle-aged men and 2–4% of middle-aged women, and it is associated with diminished quality of life, hypertension, increased cardiovascular risks, traffic accidents, and a higher mortality rate. Although a possible association has been suggested, the causal relationship remains unclear. This review aimed to systematically evaluate the available evidence on the association between SB and OSA, focusing on potential shared risk factors and underlying mechanisms. Methods: An electronic literature search was conducted in PubMed, Scopus, Web of Science, and the Cochrane Library for studies published between 2020 and 2025. Inclusion criteria encompassed observational studies and clinical trials involving adults with SB and/or OSA. Risk of bias was assessed using ROBINS-I, and the certainty of evidence was evaluated using GRADE. The review protocol was not registered. Results: A total of 11 studies met the inclusion criteria. The prevalence of SB was consistently higher in individuals with OSA compared to the general population. Several studies suggest a potential link through autonomic arousals and neurotransmitter dysregulation. However, inconsistencies in diagnostic criteria and moderate methodological quality limited the strength of the findings. Conclusions: There is a notable prevalence of bruxism in patients with OSA, suggesting possible shared pathophysiological mechanisms; however, it is necessary to standardize diagnostic criteria and conduct larger, more standardized studies to clarify the relationship. No funding was received, and the authors declare no conflicts of interest.