Background: Gastrointestinal perforations account for about 25% of acute abdominal emergencies. Despite advancements in diagnosis, management and critical care of patients due to hollow viscus perforation, the prognosis remains worrisome as the overall mortality rate due to perforation peritonitis is 6 to 27%. The aim of the study was to evaluate the prognostic value of Mannheim peritonitis index scoring system in patients with perforation peritonitis, to assess it as a clinical tool in stratifying these patients according to individual surgical risk.Methods: A prospective study of 58 patients with peritonitis due to non-traumatic hollow viscus perforation who presented to the department of general surgery, Jorhat medical college hospital, Jorhat from June 2020 to May 2021. The structured scoring system of MPI was applied along with other clinical and biochemical parameters recorded in pre-structured proforma. The study patients were divided into three groups according to MPI score. Group 1: MPI score less than 21, group 2 MPI score in between 21-29, and group 3 MPI score more than 29. Data was analysed for predicting the outcome by using IBM statistics SPSS software 21.0 version.Results: MPI scores of <21, 21-29, and >29 had a morbidity of 27.6%, 51.7% and 20.7% respectively. No mortality in patients with MPI less than 21; whereas those patients with MPI score more than 29 had the highest mortality rate of 60%. Patient with MPI score 21 to 29 had mortality rate of 40%. The number of post-operative complications, duration of ICU and hospital stay proportionately increased with the MPI score.Conclusions: MPI is an independent, disease specific, easier to calculate with very minimum basic investigations, simple and effective objective scoring system in predicting the morbidity and mortality.