Background: Delays in reperfusion therapy for myocardial infarction (MI) are associated with increased mortality and morbidity, and most of this delay is due to delay in patients initiating contact with emergency services. This study assesses the impact of the Australian National Heart Foundation media campaign and identifies patient characteristics and presenting symptoms that may contribute to delay. Methods: This prospective cohort study identified patients with a diagnosis of MI admitted to a single tertiary metropolitan hospital in Perth, Western Australia from July 2013 to January 2014. Patients were interviewed and responses were categorised to determine their reasons for delaying treatment and the impact of mass media campaigns. Delay times were analysed using multivariable linear regression models for the Whole Cohort (all patients admitted to the tertiary hospital, including patients from rural and peripheral hospitals) and the Direct Admission Cohort (patients admitted directly to the tertiary hospital). Results: Of 376 patients, 255 patients provided consent, and symptom onset-time was available for 175 patients. While almost two thirds of the cohort was aware of media campaigns, awareness was not associated with decreased prehospital delay. Median delay was 3.9 hours for the Whole Cohort and 3.5 hours for the Direct Admission Cohort. Delay was associated with being widowed, symptom onset on a weekday compared with weekend, past medical history of MI and coronary artery bypass graft, private compared with ambulance transport to hospital, and lack of symptoms of sweating and weakness. In addition, for the Direct Admission Cohort, age and income were also associated with delay. Conclusions: This study did not find an association between awareness of media campaigns and delay. This study identified important characteristics and presenting symptoms that are associated with delay, and possibly relevant to future media campaigns.