This study determined factors that influence usage of automated external defibrillation (AED) on out-of-hospital cardiac arrest among paramedics in Emergency Department of Universiti Kebangsaan Malaysia Medical Centre (UKMMC). It was a cross sectional prospective study conducted between December 2013 and January 2014. Paramedics from Emergency Department were enrolled and assessed using the self-filled questionnaire consisting of multiple sections including knowledge assessment, training and practice. In total, 53 paramedics participated in this study. Only 62% participants used AEDs previously. Not more than 83% participants admitted that they would use it if required. A positive correlation was observed between age and work experience with knowledge on AED usage (p=0.001 and p=0.005, respectively). Government’s institute graduates possess better knowledge and higher confidence level than private institutions graduates (p