Background Herpes zoster ophthalmicus (HZO) is an infectious disease that results from the reactivation of latent varicella zoster virus in the ophthalmic branch of the trigeminal ganglia. HZO manifests with herpes zoster-like symptoms such as rash with or without signs of ocular involvement. Cavernous sinus thrombosis (CST) is a life-threatening condition accompanied by signs and symptoms involving the eyes and the cranial nerves. Case We report a case of septic cavernous sinus thrombosis (caused by Streptococcus constellatus subsp. constellatus) which was masked by the simultaneous occurrence of HZO in this patient, resulting in delayed diagnosis. Conclusions CST may be obscured by HZO, prompt diagnosis and treatment is necessary when such case arrive.