Successful endodontic treatment depends on a thorough knowledge of root canal anatomy. It is well established that undetected extra roots or root canals can hinder full disinfection of the whole root canal system, thus, leaving a chance for infection and increasing the likelihood of developing apical disease. Although it was previously thought that mandibular premolars typically show one root and one root canal, considerable variations in their morphology have been found in the literature. The incidence of double-rooted or three-rooted premolars is generally low but should always be suspected especially if the pre-operative radiograph suggests abnormal root outline such as bifurcation or trifurcation. It is crucial for the dentist or endodontist to have a thorough understanding of tooth anatomy. Proper pre-operative radiographic assessment and clinical examination are essential to diagnose and plan the treatment effectively. The current case report discusses the diagnosis and conventional root canal treatment of first and second mandibular premolars with 2 and 3 roots, respectively.