The treatment of immature necrotic permanent teeth with wide open apices often poses a significant challenge for the clinician. The lack of an apical stop complicates the obturation and achievement of good apical seal in such teeth. The treatment of choice for necrotic teeth with immature root is apexification, which is induction of apical closure to produce more favorable conditions for conventional root canal filling. The most commonly advocated medicament is calcium hydroxide. But the disadvantages of long treatment time, tooth fracture risk and incomplete calcification of apical bridge have led to the development of newer biocompatible materials which can complete apexification in a single visit. Although different materials are available, Mineral Trioxide Aggregate (MTA) remains the material of choice for forming an immediate apical barrier because of its superior clinical properties and high success rate. This case series highlights the use of MTA for formation of hard tissue barrier in nonvital permanent teeth with open apices with demonstrated clinical and radiographic success.