Introduction: Labeo dyocheilus is one of the main freshwater species, significant food and game fish of Uttarakhand. Sexual dimorphism is characterized as variation in outside morphology among males and females. This research would be useful to adopt a better plan for its mono-sex culture, fish identification and to determine the eco-behaviour of fish. Objectives: Various researchers in the past about breeding biology, morphological characters and scientific taxonomy but literature gap are still present concerning sexual dimorphism. To study the age and sex-dependent morphological variation were the objectives to fulfil the literature gap. Methods: Sampling was done in Western Ramganga River Uttarakhand, for this study we use wild-got fishes and laboratory-reared fishes. Measurement of various morphometric parameters was according to protocol and analyzed statistically as well. Results: Labeo dyocheilus show sexual dimorphism at various life stages. During our examination, various findings came out about the variation mainly in colour, morphometric count and appearance of special structures in the body of fish. Colour variation was noticed differently in the different age groups of fishes and this colour variation was also found in breeding and nonbreeding fishes. A total of five morphometric characters were specifically taken for this study, which shows a positive correlation when these boundary plots are against the total length of the fish. While, various unique external appearances were found in some of the fishes mainly in pectoral, pelvic and caudal fin areas. Conclusions: Studied fish was showing age and sex-dependent sexual dimorphism in colour structure and appearances.