We sought to determine, among outpatients at one university hospital endoscopy center, rates of self-reported minor adverse events (MAEs) at 2, 14, and 30 days postcolonoscopy and to identify predictors of MAEs at Day 2 postcolonoscopy. A single-center longitudinal cohort study with follow-ups at Days 2, 14, and 30 postcolonoscopy was conducted in Montreal, Canada. Baseline self-report data included patient age, gender, gastrointestinal discomforts and other discomforts in the preceding month, and comorbidity. Intracolonoscopy procedures and the method of insufflation were obtained from endoscopy reports. Minor adverse event data were obtained by either phone or Internet survey. Multivariate logistic regression was used to identify predictors of MAEs at Day 2. Of 705 individuals approached, 420 (mean age = 58.7 years; SD = 8.4, 45.7% female) were eligible and consented to study participation, and 378 (90%) participated in at least one follow-up. At Days 2, 14, and 30, 86 (25.1%), 46 (13.7%), and 13 (3.1%) patients, respectively, experienced at least one MAE. At the Day 30 follow-up, 2 (0.53%) patients reported having experienced a serious adverse event. The multivariable analysis results showed that screening compared with nonscreening colonoscopy was protective for MAEs at 2 days (OR = 0.5, 95% CI [0.3, 0.9]). We found that 25% of patients experienced at least one MAE at 2 days postcolonoscopy, and screening compared with nonscreening colonoscopy patients were half as likely to experience these early MAEs. Nurses may use these findings to educate and reassure patients about colonoscopy risks. Large, longitudinal multicenter studies are needed to corroborate our findings.