The aim of this study is to compare the effect of a single diode laser application and agitation of EDTA with diode laser with different parameters at different time intervals on root fracture. Ninety mandibular incisors were instrumented except the negative control group. The specimens were divided randomly into 10 groups according to final irrigation procedure: (G1) non-instrumented; (G2) distilled water; (G3) 15% EDTA; (G4) ultrasonically agitated EDTA; (G5) single 1.5W/100Hz Diode laser; (G6) single 3W/100Hz Diode laser; (G7) 1.5W/100Hz Diode laser agitation of EDTA for 20s; (G8) 1.5W/100Hz Diode laser agitation of EDTA for 40s; (G9) 3W/100Hz Diode laser agitation of EDTA for 20s; and (G10) 3W/100Hz Diode laser agitation of EDTA for 40s. The specimens were filled, mounted in acrylic resin, and compression strength test was performed on each specimen. Statistical analysis was carried out using one way ANOVA and Tukey's post hoc tests (P=0.05). The statistical analysis revealed that there were statistically significant differences among the groups (P<0.05). Laser-agitated irrigation with a 3W/100Hz Diode laser for both 20s and 40s decreased the fracture resistance of teeth.