Cavernous sinus thrombophlebitis is a rare, potentially life-threatening, condition that is most often caused by gram-negative bacteria and, to a lesser extent, fungi. Mucor is an opportunistic fungus that frequently affects patients with a weak immune system. We describe a case of an adult female without diabetes who developed Mucor sphenoid sinusitis causing cavernous sinus thrombophlebitis. The patient presented with headache, diplopia, and right lateral rectus palsy. Cranial magnetic resonance imaging (MRI) showed abnormal prominent enhancement involving the cavernous sinuses associated with interspersed internal non-enhancing components indicating bilateral cavernous sinus thrombophlebitis and exuberant inspissated secretions within the left sphenoid sinus. After administering enoxaparin and intravenous antibiotics, the patient underwent endoscopic transnasal sphenoidotomy with nasal polypectomy. Culture results showed growth of mucor, for which the patient received itraconazole. Thereafter, complete resolution of headache, diplopia, and right lateral rectus palsy was observed. On follow-up, no residual neurologic deficits were noted. The repeat cranial MRI showed no abnormality involving the cavernous sinuses, with no evidence of cavernous sinus thrombophlebitis and normal paranasal sinuses. While a few case reports have been available on cavernous sinus thrombophlebitis caused by fungal sphenoid sinusitis with Mucor as the primary organism, none have involved immunocompetent individuals.