Fusion and gemination are developmental anomalies of the dental hard tissues that might require endodontic and surgical treatment for functional, orthodontic, or esthetic reasons. In this article, we report a rare case of successful endodontic management of unilateral fused mandibular second molar with a paramolar. The rarity with which this entity appears, along with its complex characteristics, often makes it difficult to diagnose and treat. The use of high-end diagnostic imaging modalities such as spiral computed tomography can help the clinician in making a confirmatory diagnosis and determining the treatment plan before undertaking the actual treatment. This case report highlights the usefulness of spiral computed tomography in accurate diagnosis and endodontic management of these unusual cases.