Desmoplastic small round cell tumour (DSRCT) is a rare tumour, usually arising in the abdominal cavity. DSRCT remains an aggressive malignancy, with a poor prognosis despite multi-modality treatments. In the published literature, there has been no patient who lived for three years or more without surgical excision. This report describes a case of DSRCT arising from the brachial plexus and successfully treated with caffeine-assisted chemotherapy. A 29-year-old male presented with pain and numbness in his left forearm. Radiological findings were suggestive of malignant tumour. Histology, immunohistochemical stain and fluorescence in situ hybridisation (FISH) results confirmed the diagnosis of DSRCT. He underwent caffeine-potentiated chemotherapy and the tumour disappeared. The tumour was not removed surgically as it was intertwined in the brachial plexus. Four years after the initial diagnosis, no local relapse and no distant metastases have been observed. Therefore, it is concluded that caffeine-assisted chemotherapy should be one of the treatment options for DSRCT.