Background. Acute coronary syndrome (ACS) morbidity and mortality is increasing in low to middle income countries (LMICs) such as Ethiopia. The shift in resources from managing communicable diseases to chronic conditions have brought about formidable health care challenges.Objective. the objective of this study was to examine the knowledge, attitudes and beliefs among ACS patients.Methods. Cross-sectional design was used to enroll participants admitted to one of 3 emergency units (EU) in Addis Ababa, Ethiopia. Knowledge, attitudes and beliefs about ACS was measured using modified ACS response index questionaries.Results. Participant’s (N=330) mean age was 57.9 ± 14.1, majority male (n= 219, 66.36%). Half of the study participants have inadequate Knowledge (n=147, 44.6%), unfavorable attitudes (n=152, 46 %), and belief (n=153, 46.4%) about ACS symptoms even after being diagnosed and treated in the EU. The most frequently recognized ACS symptoms were chest discomfort (n= 274, 83%), fatigue (n=267, 80.9%) and chest pain (n=266, 80.6%) while Jaw pain (n=101, 30%) neck pain (n=146,44.2%), were less often recognized. Nearly two thirds of the participants (n=214, 65 %) would not prefer to use emergency medical services (EMS) to come to the hospital. Factors associated with adequate knowledge were age < 45 (AOR= 2.16, CI (1.1-4.0) p=0.014), and female sex (AOR= 2.7, CI (1.5-4.4) p= 0.001) and diabetics (AOR=1.9, (1.18-3.0) p= 0.008). Meanwhile, lack of formal education (AOR=6.7, CI (3.1-14) p<0.001) and unemployment (AOR=2.0, CI (1.1-3.8) p=0.021) were associated with unfavorable attitude. In addition, lack of social support (AOR=1.9, (1.17-3.0) p=0.009) and unfavorable attitude (AOR=2.1, CI (1.3-3.4) P=0.001) were significantly associated with unfavorable belief.Conclusion. Despite receiving treatment for ACS in an EU, roughly half of participants did not have adequate knowledge, favorable attitude and belief towards ACS. This elucidates there is significant communication gap between the health care providers and patients. The study findings stipulate there is a need to provide health awareness campaigns using different media outlet with special attention to the uneducated and unemployed groups. Furthermore, most participants were less likely to utilize EMS, which should be further investigated and addressed.