Radicular cysts (RCs) are the most common inflammatory jaw cystic lesions that occur infected and necrotic in teeth pulps. They account for more than 50% of all odontogenic cysts. Radicular cysts cause slowly progressive painless swelling. There are no symptoms until they become large. Enucleating the cyst is recommended with primary treatment. Here we describe a patient with a large RC with maxillary sinus involvement who underwent an endonasal endoscopic approach for complete resection. In conclusion, the endonasal endoscopic approach should be kept in mind for the resection of RC with maxillary sinus involvement because of its minimally invasive characteristics.