Purpose The aim of the present study was to evaluate the prognostic factors that may affect the success in endoscopic cartilage tympanoplasty and determine the outcomes of endoscopic cartilage tympanoplasty. Methods This study included 312 patients who underwent transcanal endoscopic type I cartilage tympanoplasty. The effects of sex, the affected side, the size of the perforation, the location of the perforation, the absence of myringosclerosis, external ear canal protrusion, the condition of the contralateral ear, and surgical experience on the rate of graft success and hearing improvement were investigated. Results The affected side, sex, location of the perforation, myringosclerosis, the condition of contralateral ear, and surgical experience did not significantly affect the surgical success (p > 0.05). However, the size of perforation and ear canal wall protrusion were significantly related to both functional and anatomical success (p < 0.05). Conclusion Endoscopic transcanal type I cartilage tympanoplasty can be performed with a high anatomical and functional success rate. However, surgeons should be more careful and design a case-specific operation strategy in patients with external ear canal anterior wall protrusion and large perforations.