Ambulance response time is one of the key performance of ambulances services. The objective of this study is to determine the factors associated with delayed ambulance response time in Hospital Universiti Sains Malaysia (HUSM). This was a cross sectional study conducted in Department of Emergency Medicine, Hospital Universiti Sains Malaysia (EDHUSM) between January 2016 to January 2017. A total of 300 ambulance calls were included in our analysis. Data were collected by ambulance paramedic using validated ambulance form. All ambulance forms with missing data were excluded from this study. Of the 300 ambulance calls within the study periods, 254 cases (84.7%) were determined to have delayed ambulance response time. Current ambulance response time is 14 minutes with interquartile range of 5 minutes. Factors which showed significant association delayed ambulance response time include distance from hospital, location, type of emergency and ambulance mechanism. The odd of delayed ambulance response time by every increase in distance unit was 1.59 (95% CI, 1.37 to 1.85). For location type, the odd of delayed ambulance response time for public location as compared to road was 0.13 (95% CI, 0.04 to 0.45). For ambulance mechanism, the odd of delayed ambulance response time for beacon type as compared to siren type was 0.22 (95% CI, 0.01 to 0.69). Further intervention should be initiated based on our findings to improve current ambulance response time.