Our aim was to investigate whether adding ω-3 polyunsaturated fatty acids (PUFAs) to parenteral nutrition (PN) could reduce inflammation and improve immune function in patients following esophageal cancer surgery. In this pilot study, 60 patients with esophageal cancer were divided into 2 groups (30 patients in each group). All patients had total scores of more than or equal to 3 on the nutritional risk screening (NRS2002) test recommended by the European Society of Parenteral Enteral Nutrition, which showed that all patients had nutritional risk and should receive nutritional support. Both groups received isocaloric and isonitrogenous PN. One group received a ω-3 PUFAs supplement. Key indicators of inflammation [serum procalcitonin (PCT) level and the ratio of CD4(+) to CD8(+) (CD4(+)/CD8(+) ratio)] were determined intraoperatively and 24, 72, and 144 h postoperatively. PCT level was notably lower and CD4(+)/CD8(+) ratio was markedly higher in the ω-3 PUFAs group (P = 0.007 for PCT level and P = 0.012 for CD4(+)/CD8(+) ratio) on postoperative day 6 but not on postoperative days 1 and 3. ω-3 PUFAs supplemented PN can reduce inflammation and improve immune function in patients following esophageal cancer surgery. A larger trial is required to see whether ω-3 PUFAs supplementation of PN improves the clinical outcomes of patients following esophageal cancer surgery.