Gliosarcoma, which is regarded as a variant of glioblastoma, is a rare malignant neoplasm of the central nervous system. Both its sarcomatous component and glial component are reported to share significant clinical and genetic similarities. However, gliosarcomas are considered to be characterised by a lack of the BRAF V600E mutation. Here, we report two cases of gliosarcoma harbouring the BRAF V600E mutation, of which one case appears to have arisen de novo, while the other likely arose from ganglioglioma. Interestingly, the BRAF V600E mutation was detected only in the glial component in the first case, but was present in both the glial and the sarcomatous components in the recurrent gliosarcoma. Furthermore, the different mutation state of BRAF V600E in our two cases suggests that the malignant transformation of gliosarcoma might have different underlying genetic alterations and mechanisms in de novo versus recurrent gliosarcoma.