Background: The burden of modifiable risk factors in young Egyptian adults presenting with first acute myocardial infarction (AMI), sex differences, sex-age interplay, and its relationship with demographic, angiographic characteristics, and type of AMI is a good topic for discussion. Methods: The study enrolled 165 young (≤45 years old) consecutive, eligible patients diagnosed with first AMI (ST-elevation myocardial infarction, non- ST-elevation myocardial infarction), for their demographic, angiographic, echocardiographic, and laboratory investigations and gender differences. Results: Our population were 29–45 years old and 12.1% were females, most of whom had ST-elevation myocardial infarction; obesity in females and smoking in males were the most prevalent; and the younger the age of females presenting with AMI the more aggressive underlying risk factors and the more reduction in left ventricular ejection fraction. Most of the female culprit lesions were thrombotic and the severity of atherosclerotic culprit lesions correlated positively with blood pressure. Conclusions: The age paradox in young females (regarding left ventricular ejection fraction and the traditional risk factors) and the thrombotic nature of the culprit lesion mandate early intensive 1-year and 2-year preventive strategies against coronary heart disease (CHD) with special concern for obesity as the main trigger early in life with proper control of blood pressure. In males, smoking cessation programs are the main target to ameliorate the progress of CHD hand in hand with the other 1-year and 2-year preventive strategies of CHD.