Fish like other ectotherms differ widely in thermal tolerance limit and their physiological responses is entirely shaped up with the rise or fall of environmental temperature. Moreover, thermal tolerance window of fish larvae is entirely different from the adult tolerance limit. Larvae in particular are more sensitive to the thermal fluctuation compared to the adult ones. In previous studies, thermal tolerance limit of larvae was estimated by applying a wide range of warming rate starting from 0.04℃ to 60℃/h. Nevertheless, the choice of an accurate warming rate with respect to age or size of the fishes is extreme crucial for the correct estimation of critical thermal maximum (CTmax). In this study, we estimated CT max of chocolate mahseer larvae and juveniles using the dynamic method. Further, the estimation of CTmax was validated in response to different warming rate (1 to 18℃), acclimation temperature (14 to 29℃) and the age of fishes (15 dph, 35 dph and 3 month). The 13-15 dph larvae of chocolate mahseer had a lower and higher CT max of 32.1℃ and 36.7℃ in acclimation temperature of 17℃ and 23℃ respectively. Likewise, 35 dph larvae had a lower and higher CTmax of 32.2℃ and 37.1℃ in acclimation temperature of 17℃ and 23℃ respectively. The result clearly depicted that CTmax value does not differ significantly among the 15 dph and 35 dph larvae. However, for CTmax estimation of 15 dph larvae, the suggested warming rate was maximum up to 6℃/h and 35 dph larvae onwards 18℃/h warming rate could be used. Three-month-old chocolate mahseer could tolerate the temperature from 33.1℃ up to 38.4℃ in acclimation temperature of 14 to 29℃ which was significantly different from the 35 dph larvae.