Dens evaginatus (DE) is a rare developmental anomaly resulting in an extra cusp in teeth. This odontogenic malformation occurs during morphodifferentiation before the mineralization of hard tissue. We report an interesting case of an 11-yearold Asian boy who presented with acute pain and tooth mobility on permanent mandibular premolars due to bilateral DE. Radiographic evaluation revealed acute periapical radiolucency indicative of an abscess. Permanent mandibular right first premolar (an immature apex tooth) was treated with apexification while permanent mandibular left second premolar (a mature apex tooth) was treated with conventional root canal treatment. The differential treatments based on the degree of root formation led to favorable outcomes of preserving the teeth. Appropriate DE diagnosis is vital to timely treatments and positive prognosis while avoiding unnecessary extractions.