The goal of this study was to investigate to what extent acute heat exposure would affect the parameters of the power-duration relationship, i.e. CP and W′, using multiple constant workload tests to task failure, in women and men. Twenty four young physically active participants (12 men, 12 women) performed 3-5 constant load tests to determine CP and W′, both in temperate (TEMP; 18°C) and hot (HOT; 36°C) environmental conditions. A repeated-measures ANOVA was executed to find differences between TEMP and HOT, and between women and men. In HOT, CP was reduced by 6.5% (227 ± 50 vs. 212 ± 47 W), while W′ increased 12.4% (16.4 ± 4.4 vs. 18.5 ± 5.6 kJ). No significant two-way sex × temperature interactions were observed, indicating that the environmental conditions did not have a different effect in men compared with women. The intersection of the average curvatures in TEMP and HOT occurred at 137 s and 280 W in women, and 153 s and 397 W in men. Acute heat exposure had an impact on the parameters CP and W′, i.e. CP decreased whereas W′ increased. The increase in W′ might be a consequence of the mathematical modelling for the used test methodology, rather than a physiological accurate value of W′ in HOT. No differences induced by heat exposure were observed between women and men. Highlights The determination of CP and W′ was done using multiple constant workload tests to task failure and acute heat exposure induced changes in CP (decrease) and W′ (increase). The increase in W′ with acute heat exposure might be a consequence of the mathematical modelling for the used test methodology, rather than a physiological accurate value of W′. Acute heat exposure had a similar effect on performance parameters in women and men.