Mahseer is an important group of endemic game fish found in the Indian subcontinent inhabiting in streams, riverine pools and lakes. Besides commercial fishery, it also forms lucrative sport fishery in the Himalayan rivers. Samples of golden mahseer (Tor putitora) were collected from the river Kosi at Ramnagar area (lesser Himalayan region) of Uttarakhand, India during 2014-2016 to study reproductive biology and trace any changes in breeding phenology from earlier records. The observed breeding season was from July till September. In males (310-565 mm, 355-1750 g) and females (315-580 mm, 260-2500 g), GSI values surged from late June to early July and peaked in August. Absolute and relative fecundity ranged from 4217 to 8365 and from 3667 to 7348 per kg, respectively. The maximum water temperature was usually recorded in May (30.5°C) and minimum (18.4°C) in January. Sex ratio was estimated at 1:1.25 with χ 2 value of 3.20 and the difference was non-significant. The breeding phenology of golden mahseer may likely have gone through two distinct steps of transformation viz. shifting-prolongation (1911-1981) and reduction-stabilization (1981-present). Even after a probable reduction in duration of breeding season and shift (delay) in onset of breeding in Golden mahseer population of lesser Himalayan region during 1911-1981, some stabilization in breeding phenology appears to have been attained since 2000s. It is predicted that the species appears to be continuously adapting to changing climate in lesser Himalayas.