Objective: This study aimed to determine the effect of three different chelating agents on the fracture resistance of endodontically treated teeth with or without passive ultrasonic irrigation (PUI). Materials and Methods: The crowns of 70 extracted human mandibular premolars were decoronated to obtain a standard root length. Then, root canals were instrumented with ProTaper Next rotary file up to size X4. According to the final irrigation procedures, seven groups (n=10) were formed: Group 1 (control group), 6-mL distilled water with conventional irrigation technique (CIT); group 2, 3-mL 2.5% sodium hypochlorite (NaOCl) +3-mL 17% ethylenediaminetetraacetic acid (EDTA) with CIT; group 3, 3-mL 2.5% NaOCl +3-mL 10% citric acid (CA) with CIT; group 4, 3-mL 2.5% NaOCl +3-mL 1% peracetic acid (PAA) with CIT; group 5, 3-mL 2.5% NaOCl +3-mL 17% EDTA with PUI; group 6, 3-mL 2.5% NaOCl +3-mL 10% CA with PUI; group 7, 3-mL 2.5% NaOCl +3-mL 1% PAA with PUI. Finally, root canals were obturated with X4 gutta-percha cones and epoxy resin-based root canal sealer. Samples were embedded into acrylic resin blocks, and vertical loading was performed on a universal testing machine until the fracture occurred. Values were recorded in Newtons. Data were statistically evaluated using the One-Way ANOVA. Results: No significant differences were observed among the tested groups (p>0.05). Additionally, the activation of the tested chelating agents with PUI does not have any positive or negative effect on the fracture resistance of endodontically treated teeth. Conclusion: Within the limitations of this study, all tested chelating agents can be safely selected to avoid vertical root fracture.