Background: Tibia is the most commonly fractured long bone in the human body. Operative treatment is indicated for most tibial shaft fractures caused by high-energy trauma. Locked intramedullary nailing currently is considered the treatment of choice for most tibial diaphyseal fractures. The purpose of this study was to evaluate the effectiveness of intrerlocking intramedullary nailing in the management of tibial diaphyseal fractures in relation to achievement of union and functional results. Methods: This was a prospective observational study conducted on 40 patients of either sex with an average age of 41.6 years presenting to the Orthopaedic department of SHKM Government Medical College Hospital, Nalhar, Nuh, Haryana between September 2015 and November 2017, with a diagnosis of fracture shaft of tibia. All the patients underwent internal fixation with interlocking intramedullary nails. The patients were followed up for a period of 1 year. The patients were analysed for union and functional results using the Johner and Wruh’s criteria. Results: All the fractures united and the average time of union was 19.45 weeks. According to Johner and Wruh’s criteria, the results were excellent in 28(70%), good in 8(20%), fair in 3(7.5%) and poor in 1(2.5%) of the patients respectively in our study. Conclusions: Thus results of our study demonstrate that interlocking intramedullary nailing is a safe and effective surgical procedure for the treatment of tibial diaphyseal fractures.