Heat waves are extreme thermal events whose frequency and intensity will increase with global warming. As metabolic responses to temperature are time-dependent, we explored the effects of an exposure to several heat waves on the mitochondrial metabolism of zebrafish Danio rerio. For this purpose, zebrafish were acclimated at 26 ◦C or 31 ◦C for 4 weeks and some fish acclimated at 26 ◦C underwent 2 types of heat waves: 2 periods of 5 days at 31 ◦C or 10 days at 31 ◦C. After this acclimation period, mitochondrial respiration of red muscle fibres was measured at 26 ◦C and 31 ◦C for each fish, with the phosphorylation (OXPHOS) and basal (LEAK) respi- rations obtained with activation of complex I, complex II or complexes I and II. The respiratory control ratio (RCR) and the mitochondrial aerobic scope (CAS) were also calculated at both temperatures after the activation of complexes I and II. Under our conditions, heat waves did not result in variations in any mitochondrial pa- rameters, suggesting a high tolerance of zebrafish to environmental temperature fluctuations. However, an acute in vitro warming led to an increase in the LEAK respiration together with a higher temperature effect on complex II than complex I, inducing a decrease of mitochondrial efficiency to produce energy at high temperatures. Increased interindividual variability for some parameters at 26 ◦C or 31 ◦C also suggests that each individual has its own ability to cope with temperature fluctuations.