Objective Colonoscopy is a complex procedure that requires bowel preparation, sedation, and has the potential for substantial risk. Given this, we investigated colonoscopy patients' perceived and actual understanding of the procedure. Methods Consecutive colonoscopy patients were enrolled and surveyed, with their caregivers, immediately prior to their procedure. Demographics, health literacy, socioeconomic status and perceived risks/benefits were assessed. Thematic analysis was conducted on open-ended responses and a 3-level outcome variable was created to categorize correctness of patients’ and caregivers’ understanding. Multinomial logistic regression was used to determine predictors of response level. Results Patients (N = 1821) were 77% White, 60% female, and averaged 54 years old, caregivers were demographically similar. Among patients, bivariate analysis revealed that younger age, minority race, and low income, education, and health literacy were associated with incomplete understanding. Multinomial regression revealed that age, education, health literacy, first-time colonoscopy, and perceived risk-benefit difference discriminated among groups. Bivariate and multinomial results for caregivers were similar. Conclusion Patients and caregivers varied on information, understanding and misconceptions about colonoscopy. Implications are discussed for inadequate: 1. informed consent, 2. bowel preparation, and 3. emotional preparation for cancer detection or adverse events. Practice Implications Attention should be paid to patients’ understanding of the purpose, anatomy, and logistics of colonoscopy, preferably prior to bowel preparation.