Sucessful root canal treatment involves in the complete understanding of the root canal anatomy and the microorganisms involved in the disease processes. The complex anatomy of the blunderbuss canals render the clinician a major challenge during obturation. Inadequately filled root canals are the major cause of failure, achieving an adequate biological seal in such cases is very essential for the success of the root canal treatment. The aim of this case report was to describe the technique of managing a failed blunderbuss canal with MTA apexification and hence achieve a biological seal.