This case report discusses the presentation, diagnosis, and treatment of a 78-year-old patient with initials symptoms of ocular discomfort, headache, and decreased visual acuity in the left eye. Bone lysis of the sphenoid sinus was initially identified without direct vascular involvement, but subsequently, there was a swift development and progression of a pseudoaneurysm of the internal carotid artery adjacent to the lesion. Achieving an arterial occlusion of the internal carotid artery enabled the safe biopsy procedures, revealing an infection with A. fumigatus and initiating targeted antifungal therapy. Mycotic pseudoaneurysms are uncommon, yet their potentially dire progression due to the rapid growth of these lesions necessitates swift and comprehensive management.