Introduction: A contact with the venoms produced by a pelagic jellyfish type, known as Pelagia noctiluca, can induce both local and general symptoms. We report here a case of jellyfish envenomation with a mauvestinger in a diabetic patient who developed localized skin involvement, delayed systemic reaction and hyperglycemia. To our knowledge this is the first report of this kind in literature. Case Report: The patient, an adult male tourist with type I diabetes, was stung on the forehead by a mauve stinger jellyfish while swimming on the Maltese coast in summer 2012. Local symptoms were initially of an erythematous, edematous and a vesicular topical lesion in the forehead region, followed by massive eye swelling 72 hours after the incident. In addition, his normally well controlled diabetes was affected, with an unusual severe episode of hyperglycemia that did not respond readily to alterations in his insulin regime. Conclusion: Pelagia noctiluca is a jellyfish known for its strong cytotoxic properties. We hypothesize that the stress