BACKGROUND AND AIM: Post-infection irritable bowel syndrome (PI-IBS) can occur following acute gastroenteritis (AGE). This study was designed to evaluate the incidence and risk factors of PI-IBS following AGE and to validate a PI-IBS risk score. METHODS: This prospective study was performed between September 2014 and October 2016 on AGE patients by documenting their AGE severity and following up after 3 and 6 months to study the development of IBS (ROME III criteria). The risk score was calculated for all the subjects, and its discrimination ability was tested. RESULTS: Out of 136 hospitalized AGE patients, 35 developed PI-IBS after 6 months. The factors associated with PI-IBS were younger age, longer duration of AGE, anxiety, depression, abdominal pain, bloody stool, vomiting, fever, family history of IBS, and positive stool culture (univariate analysis); however, on multivariate analysis, younger age (adjusted odds ratio [AOR] 0.5; p 0.03), prolonged duration of AGE (AOR 8.6; p 0.01), and abdominal cramps (AOR 2.1; p 0.02) were the independent factors influencing its occurrence. PI-IBS occurred even after infection with Vibrio cholerae. The PI-IBS risk score was significantly higher in patients who developed PI-IBS (72.4 ± 14.48 vs. 31.56 ± 20.4, p-value < 0.001); score > 50 had a sensitivity and specificity of 91.4% and 84.2%, respectively. CONCLUSION: One fourth of AGE patients developed PI-IBS after 6 months. Factors influencing its development were younger age, long duration of AGE, and abdominal pain. The PI-IBS risk score had good predictive accuracy in our population.