The Churiyamai Tunnel that was constructed in 1917 near Hetauda is the first highway tunnel in Nepal. Therefore, this tunnel holds significant historical and infrastructural importance. Over the time, the tunnel suffered structural degradation issues, including partial collapses, developed cracks in linings, material deterioration, and water leakage in various sections. This manuscript describes the ratification work carried at this tunnel with an aim to emphasize the historical and cultural significance. In addition, the manuscript evaluates construction techniques used during its original development, identifies the causes behind the structural anomalies in the tunnel and presents the countermeasures applied to restore the functionality. The maintenance work was conducted between 2021 and 2022 where combination of modern and traditional technologies was utilized to strengthen the structural deficiencies while preserving the tunnel as a heritage structure. The study involved investigating the anomalies inside the tunnel and documenting the restoration techniques applied. It was envisaged through investigations that the tunnel suffered with development of cracks, material degradation, and water leakage. The applied countermeasures successfully restored the functionality of Churiyamai Tunnel and maintained status as a heritage site.