Mesenchymal chest wall hamartoma is an extremely rare tumor striking neonates and infants. Histologically, the tumor is composed of islands of hyaline cartilage intermixed with mesenchymal-like stroma and hemorrhagic cysts. We present a case of a congenital bilateral mesenchymal chest wall hamartoma (MCWH) in an infant boy. This extremely rare benign entity may be misdiagnosed as malignant tumor and shares features with another tumor of childhood-fibrocartilagenous mesenchymoma of bone.