The diagnosis of pulmonary leiomyosarcoma using bronchoscopy is difficult, and surgical resection is often performed for definitive diagnosis and curative therapy. We report a case of pulmonary leiomyosarcoma, successfully diagnosed using repeated transbronchial cryobiopsy (TBCB). A 69-year-old-woman was found to have an oval mass in the left hilar region extending into the left main bronchus on computed tomography (CT). All transbronchial biopsy specimens were necrotic, but repeated TBCB removed the necrotic tissue from the tumour and finally led to the diagnosis of pulmonary leiomyosarcoma. Proton therapy was administered, which caused shrinkage of the tumour. Thus, TBCB is useful for definitive diagnosis of leiomyosarcoma without surgical biopsy. Repeated TBCB can reduce tumour volume, eliminate atelectasis, and reduce the extent of radiotherapy exposure.