Objectives: To evaluate the grade of apical sealing associated with the root morphology of maxillary first molars with conventional endo-treatments using cone bean computed tomography (CBCT). Materials and Methods: The sample included 47 CBCTs. Evaluations were performed independently by one previously trained and calibrated examiner. The grade of apical sealing was evaluated (total sealing, less than 2 mm of sealing, greater than 2 mm unsealed, unsealed and oversealed). Molar angulation according to the palatal plane and the longitudinal axis (vertical, vestibular and palatal), the number of canals, the presence or absence of a second mesiobuccal canal (MB2) and root shape (straight, curved, bayonet, angled, merged, bifurcated) were also assessed. Statistical analysis was performed using the Chi-square test. Results: There were no differences in apical sealing according to root morphology, shape and molar root inclination (p>0.05). A significant association was reported between the presence of MB2 and a buccal inclination of the maxillary first molar (p = 0.048). Conclusions: Root morphology and molar angulation did not affect the apical sealing of maxillary first molars. However, the presence of the MB2 was associated with a buccal inclination of the maxillary first molar.