The present study was conducted to assess the knowledge regarding patient safety in operation theatre among operating room nurses of selected hospital, Kottayam. Objectives of the study were to assess the knowledge regarding patient safety in operation theatre among operating room nurses and to find out the association between knowledge of operating room nurses regarding patient safety in operation theatre and demographic variables. Convenience sampling technique was used to select 30 subjects from the operating room nurses of selected hospital, Kottayam. The tool for data collection was a structured questionnaire to assess the knowledge of operating room nurses regarding patient safety in operation theatre. The result showed that majority of the subjects 19(63.34%) had good knowledge, 10(33.33%) had average knowledge and only 1(3.3%) had poor knowledge regarding patient safety in operation theatre. The study findings revealed that there is no significant association between knowledge of operating room nurses regarding patient safety and selected demographic variables. From this study it is indicated that majority of the subjects had good knowledge regarding patient safety in operation theatre.