Objectives Swimmers must enter a marshalling call-room 20 min prior to racing, which results in some swimmers completing their warm-up 45 min pre-race. Since a recovery period longer than 15–20 min may prove problematic, this study examined 200 m freestyle performance after a 20 and 45 min post-warm-up recovery period. Design Eight international swimmers completed this randomised and counter-balanced study. Methods After a standardised warm-up, swimmers rested for either 20 (20 min) or 45 min (45 min) prior to completing a 200 m freestyle time-trial (TT). Core temperature (Tcore), blood lactate (BL), heart rate and rate of perceived exertion (RPE) were recorded at baseline, post-warm-up, pre-TT, immediately post-TT and at 3 min post-TT. Results Tcore was similar after the warm-up under both conditions, however, at pre-TT Tcore was greater under 20 min (mean ± SD; 20 min 37.8 ± 0.2 vs. 45 min 37.5 ± 0.2 °C; P = 0.002). BL was similar between conditions at all-time points before the TT (P > 0.05). Swimmers demonstrated a 1.5 ± 1.1% improvement in performance under 20 min (20 min 125.74 ± 3.64 vs. 45 min 127.60 ± 3.55 s; P = 0.01). Tcore was similar between conditions at immediately post-TT and 3 min post-TT (P > 0.05), however, BL was higher at these time points under 20 min (P <0.05). Heart rate and RPE were similar between conditions at all-time points (P > 0.05). Conclusions 200 m freestyle performance is faster 20 min post-warm-up when compared to 45 min probably due to better Tcore maintenance. This has implications for swim race preparation as warm-up procedures should be completed close to entering the pre-race call room, in order to maintain elevated core temperature.