Aim <p>To assess the impact of 980 nm diode laser-activated irrigation with or without EDTA on the adaptability of root canal filling in oval-shaped canals using a scanning electron microscope.</p> Methodology <p>Forty-five single-rooted mandibular premolars were assigned into three groups (<i>n </i>= 15) based on the final irrigation protocol: Conventional irrigation without activation; 980 nm diode laser without EDTA; 980 nm diode laser with EDTA. The marginal gap width (μm) and surface area (μm²) between the obturating material and the root canal were measured in the coronal, middle, and apical thirds using SEM software (ImageJ software version 1.53 t). The data was analyzed using Two-way ANOVA and Bonferroni’s post hoc tests.</p> Results <p>All groups demonstrated statistically significant differences in mean gap width and surface area (<i>p </i>&lt; 0.001) at the coronal, middle and apical root sections. Diode laser with EDTA group had the lowest gap values, followed by the diode laser group, while the conventional group recorded the highest values. Diode laser group exhibited the highest gap value in the coronal section. Additionally, significant differences in mean gap width and surface area were observed at different root levels within each group (<i>p </i>&lt; 0.001). The highest mean gap value observed in the apical section, whereas the lowest value was found in the middle section for both the diode laser with EDTA and diode laser groups. In contrast, the conventional group had its lowest value in the coronal section.</p> Conclusion <p>Activation of the 2.6% NaOCl and 17% EDTA using 980 nm diode laser improves the adaptation of the root canal filling to the canal walls.</p>