Abstract : Accreditation in health care system was found to affect patient safety, length of stay, quality of care and therefore was cost effective. However, no study has been conducted in Jordan to examine the impact of national health care accreditation programs on patient safety. The purpose of the study was to explore the impact of Jordanian national health care accreditation program on patient safety in terms of defining triggers and adverse events. A descriptive comparative study design was used. A questionnaire measuring triggers and adverse events was used for patients’ medical files (i.e. 360 files). Three accredited and three non accredited hospitals in Jordan. Patients in accredited hospitals had significantly lower length of stay compared to those in the non-accredited hospitals (M=3.62, SD=1.72 compared to M=4.08, SD=1.98); t (358) =-2.36, P<0.05. Additionally, number of triggers in the accredited hospitals was significantly higher than the number of triggers in non-accredited hospitals (M=1.70, SD=0.8 compared to M=1.13, SD=0.45); t (339.93) =2.79, P<0.01. Although number of triggers was higher in the accredited hospitals, number of events in the accredited hospitals was significantly lower than the reported events in non-accredited hospitals (M=0.36, SD=0.08 compared to M=0.48, SD=0.21); t (333.53) =-2.79, P<0.01. Indicators triggers were higher in accredited hospitals and events were lower which decreased the length of stay. The application of accreditation programs at Jordanian hospitals improve the care delivered to the patients and decrease the adverse events enhancing patients' safety.