Horner's Syndrome (HS) is a neurological syndrome characterised by the triad incomplete pupillary miosis, palpebral ptosis and facial anhidrosis, due to a lesion of the oculosympathetic pathway, formed of three neurons from the hipothalamus to the eye. Identifying its cause is a diagnostic challenge since in spite of its apparent lack of clinical importance, HS can be the first or only manifestation of a serious, or even potentially mortal disorder. We present the case of a 19-year-old male patient with a history of nonspecific ocular pains of two months evolution. He attended the emergency ophthalmological clinic where he was diagnosed with an HS as the first clinical manifestation of Hodgkin lymphoma.