Background: postoperative sore throat (POST) is the commonest complication after endotracheal intubation. The efficacy of intravenous non-steroidal anti-inflammatory drugs (NSAIDs) in alleviating postoperative sore throat has not been investigated. Objective: to evaluate the effect intravenous diclofenac sodium on the occurrence and severity of POST. Design: a randomised, double-blinded, controlled clinical trial. Setting: the operating theatres of the Aga Khan University Hospital, Nairobi, Kenya. Population: endotracheally intubated adult inpatients undergoing general anaesthesia for either general surgical or gynaecological laparoscopic surgery. Methods: forty two adult inpatients scheduled for laparoscopic surgery were randomized into two equal groups. The intervention group (referred to as the diclofenac group) received a single intravenous dose of 75mg diclofenac sodium in addition to standard care given at our hospital for the prevention of POST. The control group (referred to as the standard care group) received standard care only. All patients were interviewed postoperatively at two, six and eighteen hours. Data of the baseline characteristics, the occurrence and severity of sore throat were collected. If sore throat was present, a numerical rating scale (NRS) score was used to assess its severity. Results: the baseline characteristics of the participants were similar. The occurrence of POST at two hours postoperatively was less in the intervention group than in the standard care group, 15% and 30% respectively. However this difference did not reach statistical significance (p 0.26). There was no difference in the severity of postoperative sore throat between the intervention and standard care groups at two, six and eighteen hours postoperatively (p 0.360, 0.678 and 0.862 respectively) Conclusion: intravenous diclofenac sodium added to the standard care does not affect the occurrence or severity of postoperative sore throat.