The mountain hawk-eagle maintain their home range with a rather spectacular aerial display. Display activities tend to peak within the time period prior to breeding. Their aerial display includes conspicuous and often noisy high circling, both single and mutual, and undulating sky dance of steep dives and climbs with bubbling call uttered at each peak. Like many raptors, the display is likely largely to proclaim ownership to conspecifics but also probably has some function in reinforcing existing pair bonds. The breeding season falls between February and June in the Himalayas while in Japan, it falls from April to July. The laying dates largely correspond to early spring or colder dry season in most of their range. The pair builds a large stick nest, that can be up to across and deep (after repeated uses). Pairs may have as many as 2 to 3 nests but usually have just one. The male in the pair is said to bring most of the nest materials while female is said to primarily construct the nest. As in many accipitrids, active nests are more often than not lined with greenery, usually either green leaves or conifer sprigs. Nests are usually located at above the ground in a large forest tree, though also sometimes more isolated trees such as Deodar cedars (Cedrus deodara), which were popular in the Himalayas region. In the Indian subcontinent, sal trees (Shorea robusta) and red cedar (Toona ciliata) are favored at slightly lower elevation forests whereas deodar cedars, pines, holly, saj (Terminalia elliptica) and moru oak (Quercus floribunda) are often favored at higher elevations. Many nests are often near a steep-edged ravine, or alternately near a natural tree line, freshwater wetland or other environment that provides ample view of the surrounding area. Clutch size is usually 1 or 2 but up to 3 eggs in a clutch have been reported in Japan. It is claimed that one egg is considered the norm in most of the range, as is invariably the case in the related changeable hawk-eagle. The egg is pale clay-colored or reddish in colour with varied freckling of darker red or pure white, and often with blotches and spots of red at the large end. A sample of egg sizes in the nominate subspecies showed a range of in height, with an average of while the range in diameter was , with an average of . One egg from N. n. orientalis measured . It has been claimed that only the female will incubate and will be fed by the male. Hatching dates seem to peak around mid-March in the Indian subcontinent. At one nest, an immature male was recorded as the mate of an adult female. In another case, when the female in a pair died during nesting, the following year the male paired with another female and used a nest from the original nest.