The Nilagiri sheep is a dual utility (fine wool and meat), native to the Nilagiri hills of Tamil Nadu. It is known for its adaptability to high altitude and low input system of rearing. At present, this breed is endangered with less than a thousand numbers existing, of which about 50 percent is maintained at Sheep Breeding Research Station, Sandynallah. Efforts are on to conserve the breed in-situ. Generation interval (GI), pedigree completeness level, inbreeding coefficient (F), average relatedness (AR), effective population size (N
e), and effective number of founders (f
e) and ancestors (f
a) were studied for the breed. Pedigree analysis was carried out using data available at the research station on 5 051 animals from 1965 onwards using ENDOG ver. 4.8. Higher values of pedigree completeness (more than 80 percent for 5th generation), balance in percent of ancestors between sire and dam pathways and higher equivalent complete generations (7.12) for the reference population were indicative of the depth in pedigree. The GI, F, and AR were 3.36 years, 2.17 and 3.45 percent, respectively. N
e based on maximum number of generations and individual increase in inbreeding was 298.83 and 97.25, respectively. f
e and f
a were 59 and 41, respectively, for the reference population. F was far from critical values of inbreeding and f
a ratio indicated absence of stringent bottlenecks. The effective population size was on the higher end of the range reported for endangered sheep breeds. The knowledge on genetic diversity and effective population size coefficients would support the cause of conservation.