Otolaryngologist tends to assume that the cranial nerve palsy is due to local causes, but it is important to overlook the symptoms to rule out other neurological causes too. Here, we present a 79-year-old elderly man, diabetic, who presented to our department with ophthalmoplegia along with contrast-enhanced computed tomography scan of nose and paranasal sinuses did in another hospital showing suspected mass lesion in bilateral sphenoid sinuses with the expansion of the sinus wall and erosion of the posteromedial wall of the right orbit. A provisional diagnosis of ophthalmoplegia secondary to pressure effect from the mass lesion in the sphenoid sinuses was considered. The patient underwent functional endoscopic sinus surgery (FESS) and fungal debris was removed from the sphenoid and ethmoid sinuses on both sides. Immediate postoperative period, he had improvement in ptosis. On subsequent follow-up, there was a worsening of his symptoms and neurological evaluation done. A repetitive nerve conduction study revealed abnormal decrement in the bilateral median and facial nerves. Blood serum levels showed elevated acetylcholine receptor antibody (10 nmol/L). Thus, a diagnosis of ocular myasthenia gravis was made. The patient was symptomatically better with neostigmine (60 mg) and ophthalmoplegia improved.