An immunocompetent man in his 40s presented with 3 months of mid-thoracic back pain which progressed to include progressive paraesthesias and lower extremity weakness. Investigations revealed thoracic spine osteomyelitis with signs of cord compression. He underwent neurosurgical intervention, including laminectomy, spinal cord decompression and partial resection of an epidural mass. Initial intraoperative biopsy and surgical pathology results were concerning for an acid-fast bacillus as the causative pathogen, and the patient was given empiric therapy for presumed Mycobacterium tuberculosis. However, microbiology speciation revealed the presence of the non-tuberculous mycobacterium (NTM) Mycobacterium kansasii, which resulted in an alteration of his antimicrobial therapy. This case highlights the importance of considering NTM as a possible aetiology of spinal osteomyelitis, even among immunocompetent individuals or in low-prevalence regions.