This is the first reported case of an unusual complication of upper extremity swelling of the arm in a patient with an arterio-venous (AV) graft for haemodialysis. A graftogram demonstrated an aberrant fistula formation between the native arterial branch and the AV graft (aberrant arterio-graft fistula). Inadvertent back wall laceration of the AV graft during haemodialysis cannulation was postulated to be the aetiology. Aberrant arterio-graft fistula formation may be hard to diagnose because of the presence of thrill or bruit at the level of the anastomoses and rarity of the complication. Progression of extremity swelling with or without central venous occlusion should raise the suspicion and sought further investigation. Proper cannulation techniques prior to haemodialysis may prevent such complications.