Temperature is one of the most important abiotic factors for ectothermic animals and has been called the "ecological master factor" for fish. In the context of global climate warming, the temperature adaptability of cold-water fish has become a focus of interest and concern. Brachymystax lenok tsinlingensis, a threatened fish in Qinling Mountain region, is a second-class state-protected wild animal in the China Red Data Book of Endangered Animals, and is generally regarded as one of the two southernmost-distributed Salmonid fish worldwide. Remarkably, the lowest elevation at which B. lenok tsinlingensis occurs has risen by about 300 m, likely reflecting shifting thermal ranges in response to changing climate. Although water temperature is crucial for the survival and distribution of B. lenok tsinlingensis, information on the thermal biology of this species remains largely unknown. In this study, we investigated the effects of temperature and repeat measurement on fitness-related parameters (i.e. fast-start, swimming performance and post-exhaustion metabolic characteristics) in B. lenok tsinlingensis. The results showed that: (1) the latency time (T_latency) of fast-start in B. lenok tsinlingensis became shorter as the temperature increased (P<0.05), but temperature and repeat measurement had no significant effect on the reaction rate (R) (P>0.05). (2) Both gait transition speed (U_gait) and constant acceleration test speed (U_cat) were significantly affected by temperature (P<0.05), while those were not affected by repeat measurement (P>0.05). (3) Temperature had a significant effect on the routine metabolic rate (RMR) and the maximum metabolic rate (MMR) (P<0.05), but had no significant influence on the metabolic scope (MS) (P>0.05). Besides, the MS and MMR were not significantly affected by repeat measurement (P>0.05). (4) The Q₁₀ values of physiological parameters was larger in the direction of low acclimation temperature (6-12℃), and smaller in the direction of high acclimation temperature (12-18℃). The results indicated that: (1) B. lenok tsinlingensis could react more rapidly at high temperature, but it mainly adopted the strategy of "keeping still" rather than escaping in response to the low-intensity mechanical stimulation. (2) The swimming performance of B. lenok tsinlingensis was sensitive to temperature changes, and the optimum temperature for swimming performance was estimated to be between 12℃ and 18℃. (3) B. lenok tsinlingensis showed excellent performance in metabolic recovery and repeat swimming performance, however, due to the relatively weak swimming ability of this species, it may be vulnerable to changes in habitat water temperature and flow environment.