Hoffmann syndrome is a rare form of hypothyroid myopathy characterised by muscle weakness, stiffness and pseudohypertrophy. Here we report an otherwise healthy 31 year old male (BMI 24) who presented with progressive headaches, myalgias, muscle fatigue, dry skin, mental lethargy, weight gain of 5 kg within 3 months following administration of the influenza vaccine. Examination revealed temporal muscle hypertrophy, reduced relaxation of deep tendon reflexes without neck swelling or masses. Further investigations revealed markedly elevated TSH (220), Creatinine (156), Creatine kinase (2537), TSH-receptor antibodies and thyroid peroxidase antibodies with reduced free thyroxine levels (3) and eGFR (50). Following introduction of supplemental thyroxine therapy (100mcg OD) the patient’s symptoms improved and serum levels of Creatine and creatinine normalised. Thyroid function rebounded to transient hyperthyroidism, resulting in a short course of Carbimazole (10mg OD) which was progressively weaned off until the patient’s antibody levels and thyroid function normalised. This is the first case of vaccine induced Hoffmann syndrome reported in the literature.