The success of endodontic treatment relies on both apical and coronal sealing. To achieve a good three-dimensional seal, the removal of the smear layer becomes mandatory. This study aims to assess the difference in debris accumulation and smear layer formation while using automated root canal irrigation and conventional syringe needle irrigation. Single-rooted human mandibular premolar teeth (n = 30) which were indicated for orthodontic extractions were selected. An endodontic access cavity was prepared, and a glide path was created. Based on the irrigation protocol decided upon for the study, the teeth were randomly allocated into three study groups, namely Group 1, where the manual syringe needle irrigation method was adopted; Group 2, in which automated root canal irrigation was undertaken; and Group 3, in which teeth remained un-instrumented as it was considered the Control group. The teeth were decoronated at the cement-enamel junction (CEJ) and were subjected for scanning electron microscopy (SEM) examination. Debris and smear layers were viewed in 1000× magnification and scored. A statistically significant (p < 0.05) lower mean debris and smear layer score (p < 0.05) was observed in both study groups when compared with the control group. However, no significant difference (p > 0.05) in the debris and smear layer was observed between the manual syringe needle irrigation and automated irrigation, although automated irrigation devices can be a potential alternative. The present study concluded that the efficacy of smear layer removal remained the same with both automated irrigation and manual syringe irrigation.