Bloody nipple discharge occurs rarely in infancy and may be secondary to mammary ductal ectasia. Discharge commonly resolves spontaneously, and ultrasonography is a useful diagnostic technique to detect the cause of discharge. We report a 28-month-old boy who presented with unilateral bloody nipple discharge for one month without signs of infection or mass. Ultrasound examination showed a dilated duct in the retroareolar region. No atypical cells were present on cytologic evaluation of the discharge. Further diagnostic studies were avoided and the discharge ceased completely one month later. We conclude that bloody nipple discharge is usually a benign and self-limited process in infancy and that it is advisable to avoid unnecessary invasive investigations initially. Invasive diagnostic studies or surgery should be reserved for cases with a palpable mass, persistent discharge or equivocal ultrasonographic findings.