BACKGROUND: Cold fluid ingestion is recommended during work to maintain hydration status and physiological function. While monitoring the physiological strain index (PSI) during work in the heat is recommended, it is logistically challenging. Subjective estimates, i.e., perceptual strain index (PeSI), are thought to reflect PSI. However, it remains unclear if cold fluid influences an individual's perception of heat strain. METHODS: Twenty young adults (10 females) performed four 15-min bouts of moderate-intensity (200 W/m FINDINGS: Tc, HR, TS and RPE were not influenced by fluid temperature (P ≥ 0.09), nor was the relation between PeSI and PSI (P = 0.11). Mean bias [95% LoA] between PSI and PeSI was greater in cold (-2.1 [-5.7 - 1.5]) compared to the warm fluid condition (-1.8 [-4.8 - 1.2], P = 0.008). CONCLUSION: While the relation between PeSI and PSI was not influenced by beverage temperature the agreement between measures was worsened following cold fluid ingestion.