Abstract Introduction Atrial cardiopathy is one of the most common potential sources of thromboembolism for embolic stroke of undetermined source (ESUS). The study aims to investigate the incidence of atrial cardiopathy (defined by severe left atrial enlargement (sLAE) or elevated serum N‐terminal pro‐B‐type natriuretic peptide (NT‐proBNP) > 250 pg/ml) in patients with ESUS and compare with other stroke subtypes. Methods We retrospectively collected data of 936 consecutive patients with diffusion‐weighted imaging‐confirmed acute ischemic stroke. The incidence of atrial cardiopathy was examined in ESUS, large artery atherosclerosis (LAA), and small vessel disease (SVD) strokes. Clinical characteristics were compared between ESUS patients with atrial cardiopathy (AC‐ESUS) and patients with atrial fibrillation‐induced cardioembolism (AF‐CE) stroke. Results 245 patients were diagnosed with ESUS, while others were diagnosed with LAA ( n = 312), SVD ( n = 258), and AF‐CE ( n = 121) strokes. The incidence of sLAE in ESUS patients was higher than in LAA or SVD group (5.3% vs. 1.6% and 1.2%, respectively, p = .005) and higher than in combined LAA/SVD group (5.3% vs. 1.4%, p = .001). The incidence of elevated serum NT‐proBNP in ESUS patients was not statistically different from that in LAA or SVD group. Compared with patients with AF‐CE stroke, AC‐ESUS patients had milder manifestations, had less hemorrhagic transformation, had better short‐term outcome, and had fewer in‐hospital complications. Conclusions The incidence of sLAE was higher in ESUS patients than in patients with noncardioembolic strokes. AC‐ESUS was milder when compared to AF‐CE stroke.