Aim: The aim of the study was to compare the analgesic effects of ketamine over fentanyl combined with propofol in analgesia-based elective colonoscopy with purpose of patient safety and satisfaction. Methods: This is a double-blinded prospective randomized controlled trial. Ninety patients were included and randomized to either fentanyl-propofol (Group FP, n : 30), ketamine-propofol (Group KP, n : 30) or propofol-control group (Group C, n : 30). Group FP patients received fentanyl and propofol, Group KP received ketamine and propofol and Group C, propofol. In all groups, incremental doses of propofol were used to maintain a Ramsay sedation score (RSS) of 5. Respiratory depression and hemodynamic parameters were monitored for the first minute and every 5 min during endoscopy. Fifteen minutes after the procedure, the degree of pain was assessed using a visual analog scale (VAS), the quality of recovery according to the Aldrete score (ARS), complications during and after the procedure and additional doses of propofol were recorded. Results: Mean arterial pressure (MAP) at 5 and 30 min ( p < 0.05), heart rate (HR) at 15, 25 and 30 min ( p < 0.05) and peripheral oxygen saturation (SpO 2 ) at 30 min ( p < 0.05) were statistically significant for Group FP. Desaturation (* p = 0.033), and weakness (* p = 0.004) was also significant for Group FP at 20, 25 and 30 min ( p < 0.05). Pain was lower assessed for the Group KP according to the VAS (** p = 0.025). Conclusion: In analgesia-based colonoscopy, ketamine provides appropriate analgesia and less incidence of complications compared to fentanyl.