The purpose of this study was to explore the effect of individualised sodium bicarbonate (NaHCO3) supplementation according to a pre-established individual time-to-peak (TTP) blood bicarbonate (HCO3 -) on 4-km cycling time trial (TT) performance in the heat. Eleven recreationally trained male cyclists (age: 28 ± 6 years, height: 180 ± 6 cm, body mass: 80.5 ± 8.4 kg) volunteered for this study in a randomised, crossover, triple-blind, placebo-controlled design. An initial visit was conducted to determine TTP HCO3following 0.2 g.kg -1 body mass (BM) NaHCO3 ingestion. Subsequently, on three separate occasions, participants completed a 4-km cycling TT in the heat (30 degrees centigrade; °C) (relative humidity ~40%) following ingestion of either NaHCO3 (0.2 g.kg -1 body mass), a sodium chloride placebo (0.2 g.kg -1 BM; PLA) or no supplementation (control; CON) at the predetermined individual TTP HCO3 -.Absolute peak [HCO3 -] prior to the 4-km cycling TT's was elevated for NaHCO3 compared to PLA (+2.8 mmol.l -1 ; p = 0.002; g = 2.2) and CON (+2.5 mmol.l -1 ; p < 0.001; g = 2.1). Completion time following NaHCO3 was 5.6 ± 3.2 s faster than PLA (1.6%; CI: 2.8, 8.3; p = 0.001; g = 0.2) and 4.7 ± 2.8 s faster than CON (1.3%; CI: 2.3, 7.1; p = 0.001; g = 0.2). These results demonstrate that NaHCO3 ingestion at a pre-established individual TTP HCO3improves 4-km cycling TT performance in the heat, likely through enhancing buffering capacity.