Brain-derived neurotrophic factor (BDNF) is a neurotrophic factor highly expressed in coronary plaques, particularly in macrophages, and in activated platelets. Thus, a possible role in the pathogenesis of acute coronary syndrome (ACS) has been suggested. We evaluated systemic BDNF levels according to the different clinical presentations of ACS. Moreover, we assessed the relationship between BDNF levels and the presence of optical coherence tomography (OCT)-defined macrophage infiltrates (MØI) and healed plaques along the culprit vessel. We enrolled consecutive patients presenting with ST-elevation myocardial infarction (STEMI) or non-ST-elevation (NSTE)-ACS. Serum BDNF levels were assessed by enzyme-linked immunosorbent assay. Plaque characteristics of the culprit vessel were assessed by OCT. Among 126 ACS patients (median age 68.00, interquartile range [IQR] 59.75–75.25 years, male 74.6%, 71 (56.3%) were NSTE-ACS and 55 (43.7%) were STEMI. BDNF levels were higher in STEMI patients compared to NSTE-ACS. OCT assessment was performed in 53 (42.1%) patients. Patients with MØI (n = 27) had higher BDNF levels compared to patients without MØI. Furthermore, patients with healed plaques (n = 13) had lower BDNF levels than patients without healed plaques. At multivariate regression analysis BDNF levels independently predicted the presence of MØI (odds ratio [OR] = 2.856; 95% confidence interval [CI] [1.151–7.090], P = 0.024) and the absence of healed plaques (OR = 0.438, 95% CI [0.185–0.992], P= 0.050). Among ACS patients, BDNF levels were higher in patients with STEMI. Moreover, BDNF levels were independently associated with MØI and with the absence of healed plaques along the culprit vessel, suggesting a possible role of BDNF in promoting plaque inflammation, destabilization and occlusive thrombosis.