We report the rare occurrence of bilateral asymmetrical mucoceles of the paranasal sinuses that resulted in a unilateral orbital complication. The patient was a 47-year-old woman who presented with complaints of diplopia, blurred vision, and protrusion of her right eye that had progressed over a period of several months following an upper respiratory tract infection. Computed tomography detected the presence of two large, asymmetrical mucoceles. The lesion on the right involved the frontal and ethmoid sinuses, and the one on the left involved the ethmoid sinus. The mucoceles were locally expansile and had eroded the surrounding bony structures on the right. The expansile nature of the right-sided mass had displaced the right orbit, which was the cause of the vision deterioration. Transnasal endoscopic surgery was performed to excise and marsupialize the mucoceles. This modality was preferred over conventional open surgery because it affords good visualization, it is safe, and it is a less morbid procedure. The patient's recovery was uneventful, and she was discharged home on the third postoperative day. On continuing follow-up, her vision had improved, her intraocular pressure had returned to normal, and her orbits were in their normal position. Based on our literature search, no case of bilateral frontal and ethmoid sinus mucoceles has been previously reported.