The presence of digestive fistula involves chronic inflammation and fibrosis. It has been reported that ω3-polyunsaturated fatty acids stimulate the resolution of inflammation. Determine if the administration of oral ω3 reduces fistula output and the time required for fistula closure. Forty-nine patients with postoperative fistula were randomly divided in two groups: 26 received conventional treatment and 23 received the conventional treatment supplemented with ω3 (540 mg eicosapentaenoic acid and 360 mg docosahexaenoic acid) for 35 days. Patients were monitored daily for fistula output and spontaneous closure. Additionally, serum pro-inflammatory cytokines and C-reactive protein were quantified in four patients with conventional and in seven patients with ω3 treatment. Patients with ω3 had significantly decreased fistula output from days 2 to 27, compared to control (p