Objective: This study aimed to evaluate acute coronary syndrome (ACS), serum procalcitonin levels, Platelet/Mean Platelet Volume ratio (PMR) and Neutrophil/lymphocyte ratio (NLR) concerning post-myocardial infarction (MI) complications, mortality, and morbidity. Material and Method: The study included a total of 913 patients with ACS who presented to the emergency department with chest pain between January 2013 and December 2017. The patients were categorized as ST-elevated MI (STEMI), non-ST elevated MI (NSTEMI) and unstable angina (UA) according to the diagnosis. The demographic and laboratory characteristics of the patients were compared for three-vessel disease (TVD) and mortality rates. Result: Post MI complications, TVD, and mortality were significant among acute coronary syndrome groups. The three-vessel disease was mostly observed in anterior MI with a maximum rate of 58 (39.7%). Mortality was found as 23 (16.3%) in anterior MI and 18 (12.2%) in NSTEMI. Serum procalcitonin levels were highest in anterior MI. Platelet to Mean Platelet Volume ratio was higher in UA, whereas it was lower in STEMI and NSTEMI. Neutrophil to lymphocyte ratio was the lowest in UA. The cTn I values of STEMIs at 0, 6, 12 hours were higher than UA, and the 12th-hour cTnI values in anterior MI were higher than NSTEMIs. It was found that procalcitonin and NLR had a positive correlation with post-MI complications, mortality, and TVD, whereas PMR exhibited a negative correlation. Conclusion: The levels of procalcitonin, PMR, and NLR may be significant in respect of post-complications, mortality, and morbidity in acute coronary syndrome.