Background: Cardiovascular incidents are a common cause of death around the world. Acute myocardial infarction (AMI) poses high risks for the patient due to plaque rupture or erosion along with a superimposed non-occlusive thrombus; therefore, timely treatment with antithrombotic agents plays a key role in reducing an AMI mortality rate. Objectives: The present study aimed to assess the time interval between the admission of AMI-suspected patients and treatment initiation. Patients and Methods: This cross-sectional study was conducted on 110 patients admitted to the emergency department of Imam Hussein hospital in Tehran, Iran. Data were collected using checklists, completed by the patients’ next of kin or the emergency staff. To analyze the data, student t- test and analysis of variance were used. Results: In this study, 31 female and 79 male subjects were included, respectively. The mean time to receive the first dose of streptokinase was 66.39 minutes (73.74 minutes for females and 63.5 minutes for male patients), varying from 49.92 minutes in the morning to 69.78 minutes in the afternoon and 72.68 minutes during night shifts. Conclusions: The door-to-needle (DTN) time, in a standard setting, is recommended to be less than 30 minutes. According to the results of this study, the DTN time is comparatively two times longer in females and afternoon and night shifts. Different variables including emergency staff, physicians, patients’ characteristics, and environmental/physical factors induced this difference.