This study assessed the feasibility and effectiveness of jejunal feeding (JF) after surgery due to secondary peritonitis or failed conservative therapy of severe pancreatitis. Of 60 patients, 30 were randomly assigned to receive postoperative JF and the remaining 30 constituted the control group. Acute Physiology and Chronic Health Evaluation II, nutritional intake, systemic inflammatory response syndrome, and outcomes were measured. Patients in JF group received the daily mean of 1294.6 (362.6) kcal including 830.6 (372.7.0) kcal enterally, versus 472.8 (155.8) kcal daily in the control group (P < 0.0001). There were fewer complications in the JF patients, with no significant difference; length of stay in the intensive care unit and in the hospital did not differ. The frequency of systemic inflammatory response syndrome was similar in both groups, but outcomes differed. The first surgical intervention resulted in 3.3% of relaparotomies in JF patients, caused by unresolved peritonitis, versus 26.7% in the control subjects (P = 0.03). Recovery of bowel transit took significantly less time in the JF patients (mean: 54.6 h versus 76.8 h in control subjects, P = 0.01). JF resulted in 3.3% mortality as opposed to 23.3% in the control group (P = 0.05). In conclusion, JF is feasible and effective in postoperative treatment of patients due to secondary peritonitis or severe pancreatitis. Improved bowel and peritoneal function could be the main impact of JF.