Abstract Introduction Streptococcal myositis is a rare form of infectious myositis caused by Lansfield A beta-haemolytic streptococci. It is characterised by rapidly spreading inflammation that can result in severe systemic toxicity and necrosis of the affected tissue if not diagnosed and aggressively treated. Presentation We report a case of a 42-year-old male who presented with a one-week history of worsening right axillary swelling that progressed to painful swelling of his arm. Inflammatory markers were significantly elevated with a white cell count of 17 ×109/L and C-reactive protein of 212 mg/L. On examination, a fluctuant axillary swelling was appreciated, and a decision was made for incision and drainage under general anaesthetic. Intraoperative aspiration of his arm revealed copious purulent fluid prompting intraoperative orthopaedic consult and exploration of the anterior compartment in which there was extensive involvement of the biceps muscle. The microbiological analysis revealed gram-positive cocci in chains, and microbiology advice sought for tailoring of antibiotic regimen. He has recovered well. Discussion Though uncommon, the emergency general surgeon should have a high degree of suspicion when evaluating soft tissue infections to avert potentially disastrous outcomes. Conclusion Early diagnosis, aggressive management with high-dose intravenous antibiotics, and surgical debridement are principles to treat this rare, life-threatening infection.