Purpose: Patients with digestive system cancer frequently over-express inflammatory cytokines after surgical operations or chemotherapy. Omega-3 fatty acids are key nutrients with numerous beneficial anti-inflammatory effects in cancer patients. The anti-inflammatory effect of supplementation with omega-3 fatty acids in patients with digestive system cancer requires further validation.Methods: The meta-analysis includes studies that compared the variations in inflammatory marker (interleukin-6, tumor necrosis factor-alpha, and C-reactive protein (IL-6, TNF-α, and CRP)) concentrations between patients with digestive system cancer who were supplemented with omega-3 fatty acids versus controls who were not supplemented with omega-3 fatty acids.Results: Our findings indicated that the variations in the IL-6 and CRP concentrations in patients with digestive system cancer did not differ between the supplementation groups and the controls. Statistically significant differences in the variations in the TNF-α concentrations were observed between the supplementation groups and the controls. However, there were no significant differences in the variations in the TNF-α concentrations according to the subgroup analysis.Conclusions: Omega-3 fatty acids may have an inhibitory effect on postoperative TNF-α elevation in patients with digestive system tumors, but additional supporting data require a large clinical trial.