“Poland’s syndrome” is a rare congenital disease whereby defects can accompany the chest, nipple, chest wall, and extremities on one side of the body. We diagnosed a 19-year-old male patient who presented to another hospital for a routine physical exam before enlisting in the military and was suspected of having a left brachial plexus injury. His chief complaint was the flatness of the left anterior chest wall without any significant functional inconvenience. Aplasia of the pectoralis minor and costosternal portion of the pectoralis major was observed through physical examination and computed tomography (CT). The patient was diagnosed with left-sided Poland’s syndrome without any limb abnormalities. Poland Syndrome should be highly considered in patients presenting with bilateral chest wall imbalance in the absence of with a recent traumatic history.