Background This study investigated neutrophil activation and neutrophil-derived extracellular traps formation in coronary artery ectasia. Methods We enrolled 90 patients who underwent coronary angiography, and included 30 patients with coronary artery ectasia (CAE), 30 patients with obstructive coronary artery disease (CAD) and 30 patients with normal coronary arteries (CON). Intra-neutrophil mean myeloperoxidase index (MPXI) was determined using an automated blood cell counter (ADVIA2120 Hematology System). Serum concentrations of plasma adhesion molecules, cytokines, and neutrophil-derived extracellular traps were quantified. Results The intra-neutrophil mean myeloperoxidase index was reduced in CAE patients compared to CAD and CON patients (1.02 +/- 3.01, 3.22 +/- 3.03, 3.52 +/- 4.25, respectively; CAE vs CAD, p = 0.016 and CAE vs CON, p = 0.007). Multiple logistic regression analysis showed that MPXI and dsDNA were independent factors that predicted the presence of CAE. CAE patients had higher levels of plasma adhesion molecules (P-selectin glycoprotein ligand-1, E-selectin, L-selectin) and interleukin 1 beta levels. Neutrophil extracellular trap concentrations were significantly higher in the CAE group compared to CAD and CON patients (284.31(258.33-449.91) ng/mL, 225.12(203.34-257.13) ng/mL, and 247.37(231.04-273.01) ng/mL, respectively; CAE vs CAD, p = 0.000 and CAE vs CON, p = 0.001). Conclusions Peripheral neutrophils from CAE patients were activated and neutrophil extracellular traps were elevated in the plasma. IL-1 beta and soluble adhesion molecules may be the causal factors for neutrophil activation.