Chondromyxoid fibroma is a rare benign bone tumor observed in less than 1% of all bone tumors. Pathological diagnosis remains difficult. All bone sites may be involved with a predominance of the metaphysis of long tubular bones, particularly the proximal tibia. The tumor has been rarely reported in ribs. We present of case of chondromyxoid fibroma observed in this unusual location in a 31-year-old woman. Routine chest x-ray and computed tomography revealed an expansive destructive mass with a lobulated contour which arose in the fourth left rib. Local resection was performed and the histological examination showed benign chondromyxoid fibroma. The clinical outcome was favorable without recurrence after 15 months follow-up.