Background: Day case surgery services are increasing all over the world. The prevalence of postoperative pain after day surgery is found to be high. Little is known about the prevalence of postoperative pain, in Kenya, after day case surgeries. Objective: To investigate the prevalence of postoperative pain after day surgery at Aga Khan University Hospital (AKUH), Nairobi, to determine the severity/intensity of postoperative pain following day case surgery Methods: Consecutive sampling was carried out until sample size of one hundred and fifty patients was achieved. The purpose and nature of the study was explained to patients before informed consent was obtained. They were shown how to score their pain using a visual analogue scale prior to the surgical procedure. A questionnaire was used to collect data from the patients. Follow up information was obtained through telephone interviews at 24 and 48 hours, after discharge from the day surgery unit. Results: The prevalence of postoperative pain after day care surgery was found to be 58% within 30minutes postoperatively, 55.3% after 24 hours, and 34.7% after 48 hours following surgery. The prevalence of moderate to severe postoperative pain was 13% after 24 hours, and 11.7% after 48 hours. Conclusion: The overall prevalence of postoperative pain after day surgery at the Aga Khan University Hospital, Nairobi was noted to be different from what has been reported in the literature. The prevalence of moderate and severe pain however, is less than reported in the literature.