Leiomyosarcomas (LMS) are rare malignant tumors that are mesenchymal in origin. leimyosarcomas constitutes 7% of soft tissue sarcomas. LMS is usually found in the retroperitoneum and extremities, in adults aged 50-70 years whereas chest-wall LMS is rare. 58 years old, male patient was evaluated for right-sided thorax wall lump. The computed tomography (CT) scan of chest reveald a right-sided mass 11.5x8.7x12.8 cm in size which was continuous laterally to the 4th-8th rib and cause a minimal defect in the 5th costal cortex, with intrathoracic extension through between the 5th and 6th intercostal space. PET-BT scan didn’t show any extrathoracic spread. 3rd, 4th, 5th, 6th and 7th ribs were resected with wide negative margin. After that, thoracal wall reconstruction was performed by using 3 titanium bars and prolene mesh. Post-op period was unremarkable. The pathology of the patient was reported as leiomyosarcoma,11 cm in diameter with a high mitotic index. Primary Leiomyosarcomas of the chest wall are rare tumors. Currently, the best option for local control of the tumor is surgical resection with wide negative margin.