The comorbidity rate of metabolic dysfunction-associated steatotic liver disease (MASLD) and chronic hepatitis B (CHB) is steadily increasing. Both MASLD and CHB can independently lead to adverse outcomes, including cirrhosis and hepatocellular carcinoma (HCC). However, the impact of coexisting MASLD on HCC risk in CHB patients shows high heterogeneity across current studies: some studies suggest that MASLD may accelerate disease progression through mechanisms such as metabolic inflammation, lipotoxicity, and insulin resistance, interacting with the chronic inflammation induced by hepatitis B virus (HBV); conversely, some studies report that hepatic steatosis is associated with lower viral replication levels and a higher rate of hepatitis B surface antigen (HBsAg) clearance, indicating a potential protective effect. This review outlines the potential mechanisms underlying MASLD and CHB interactions, focuses on the divergent findings from existing clinical research regarding whether MASLD exerts a “promoting” or “protective” effect on HCC risk in CHB patients, and summarizes factors that may contribute to this heterogeneity, including the definition evolvement of fatty liver disease, differences in virological status and antiviral treatment, degree of liver fibrosis, and inconsistency in diagnostic methods and population characteristics. In the future, active intervention should be taken to address metabolic abnormalities in patients with the aforementioned comorbidities. Meanwhile, studies based on unified definitions, precise stratification, and methodological standardization should be conducted to clarify the true impact of different metabolic phenotypes on CHB progression and HCC risk, thereby providing evidence-based support for precise risk prediction and integrated intervention.