<p>High fish consumption has been associated with a reduced risk of depression. In this study, we examined the association between the frequency of blue fish intake of healthy participants and ¹⁸F-fluorodeoxyglucose (FDG) uptake using positron-emission tomography (PET). Data were extracted from a questionnaire on the frequency of blue fish intake, clinical assessments of depression using the Beck Depression Inventory (BDI), and ¹⁸F-FDG PET images. Sixty-two participants were grouped based on the frequency of blue fish consumption: more than 2 or 3 days per week (frequent intake group; F-Fish group) and once per week or less (infrequent intake group; IF-Fish group). A two-sample t-test and chi-square test were used for continuous and categorical variables, respectively. Furthermore, a two-sample t-test was performed to assess the difference in ¹⁸F-FDG uptake between the F-Fish group and the IF-Fish group using Statistical Parametric Mapping 12. The F-Fish group exhibited significantly lower BDI scores than the IF-Fish group. Whole-brain analysis revealed a cluster with significantly lower ¹⁸F-FDG uptake in the right cerebellum VI in the F-Fish group than in the IF-Fish group. In conclusion, the frequency of blue fish consumption is associated with the function of the right cerebellum VI. Further studies are warranted to clarify the mechanism underlying the preventive effect of blue fish consumption on depression.</p>