Introduction: Modern dentistry includes all the recent technical and scientific advancement in endodontics for the retention and functional stability of the tooth. Unfortunately, not all treatment results in desired results. Probably the reason being, the root canal treatment falling short of the acceptable standards. To explore the contributing factors for the failure of root canal treatment various methods have been tried such as radiographic methods, histological examinations, root clearing technique, computerized tomography etc. Aim: To assess the probable reasons for the failure of root canal treatment using radiographic and clearing technique. Methodology: After the approval of institutional ethical committee (IEC). Clinical and radiographic evaluation of fifty patients with failed root canal treatment was done. The teeth with poor prognosis were advised extraction. The extracted teeth were then stored in 10% formalin saline until use. Further evaluation was done using the clearing technique, followed by the analysis of the cleared teeth using stereomicroscope in 20X magnification to assess the cause of unsuccessful root canal treatment. Result: There was no statistically significant difference between radiographic and clearing technique. The procedural like inadequate obturation, defective coronal seal, fractured instrument, and missed canals was reported in the present study. Conclusion: While carrying out the endodontic treatment it is important to give attention to details that not only improves the endodontic quality but also maximizes the success. Regular follow ups are essential for assessing the outcome and to monitor any changes. However, clinical attentiveness during the endodontic treatment phase could potentially benefit both ;the clinician and the patient.