Cor triatriatum is a rare congenital cardiac anomaly, characterized by a fibromuscular partition dividing the left (cor triatriatum sinister) or, rarely, the right atrium (cor triatriatum dexter). Occurring in 0.1–0.4% of congenital heart disease cases, it exhibits diverse clinical presentations, often mimicking mitral stenosis and left-sided heart failure, while occasionally remaining asymptomatic into adulthood. The embryological origin of cor triatriatum remains controversial. Recent years have seen the emergence of new classification systems that offer enhanced prognostic insights. Transthoracic echocardiography is the diagnostic cornerstone. Surgical resection, preferably under cardiopulmonary bypass, is the mainstay treatment, and is associated with favorable long-term outcomes.