Osteochondroma arising from the rib is rare. They arise as bony outgrowths from the rib and extend either extrathoracically into the subcutaneous plane or intrathoracically compressing the lung or mediastinal structures. A 23-year-old male patient presented with complaints of breast lump since last year. On clinical examination, a hard bony projection with lobulated contour was palpable. Chest radiograph and contrast-enhanced CT showed a bony outgrowth arising from the anterior aspect of costochondral junction of the right fourth rib with displacement of pectoralis major muscle anteriorly. Osteochondroma should be considered as a differential diagnosis in the presentation of hard lump in the breast along with other chest wall tumors.