The most common tumours in the brachial plexus are benign schwannomas, followed by neurofibromas and malignancies, originating from the peripheral nerve sheath. The clinical manifestations of brachial plexus tumours are variable according to their location, extension, neurological elements involved and pathology. Brachial plexus tumours are rare in the upper extremity, and axillary schwannoma is uncommon. This case reports a 59-year-old woman with a tumour in her left axilla for two years, gradually enlarging with numbness in her left little finger. Microsurgical interfascicular dissection operation was performed to remove the tumour. Νumbness disappeared after the procedure, and no tumour recurrence was observed during the 30-month follow-up. To the best of our knowledge, plexiform schwannoma of the brachial plexus in the axilla has not been reported so far. In this article, such a case is reported, where this tumour was diagnosed by the histopathological examination and confirmed with immunohistochemistry.