Becker's nevus is a unilateral hyperpigmented area of skin with geographical borders. It is usually located on shoulders, anterior chest, scapular region and upper arms. Sometimes it shows evidence of androgen hypersensitivity and co-localizing with other developmental anomalies. We report a 12-year-old girl with clinical and histopathological findings compatible with Becker's nevus on her left chest accompanied with ipsilateral breast hypoplasia.