The topography of Longleng is rugged and undulating. There are no large plains; the landscape is a continuous series of steep ridges, deep gorges, and narrow V-shaped valleys. The town is situated at an elevation of approximately 1,066 meters (3,497 feet), though peaks in the surrounding district reach higher altitudes.
The soil is primarily argillaceous (clay-like) and rich in organic matter due to the dense forest cover, making it well-suited for specific types of hill agriculture. Landslides can be a common topographic challenge during the heavy monsoon season due to the steep gradients of the hillsides.