Purpose: The aim of this study was to investigate the physiological responses during upper-body aquatic exercises in older adults with different pool temperatures. Method: Eleven older men (aged 65 years and older) underwent 2 identical aquatic exercise sessions that consisted of 3 upper-body exercises using progressive intensities (30, 35, and 40 metronome beat · min[superscript -1]) on separate visits. Water temperatures for the visits were 28°C (cold water [CW]) and 36°C (hot water [HW]), and water depth ranged from 1.2 m to 1.4 m. Measurements for heart rate (HR), blood pressure (BP), oxygen consumption (VO2), and rate of perceived exertion (RPE) were compared between the CW and HW conditions. Results: The comparison between temperatures showed a higher HR response during exercise in HW, particularly when participants exercised at the highest intensities. During a 30-min postexercise period in resting conditions, HR was statistically significantly higher for the HW condition compared with the CW condition, with a large effect size (15.9%, d = 1.23). Systolic and diastolic BPs were found to be lower for the HW condition ( -7.2%, d = -0.60; -10.1%, d = -0.65), while VO[subscript 2] and RPE showed no differences. The effect size between double products (HR · systolic BP) for the 2 conditions was small (CW = 8,649 ± 1,287, HW = 9,340 ± 1,672; d = 0.36), suggesting similar myocardial oxygen requirements. Conclusion: This study showed that HR response was higher in an HW condition for older men. Warmer environments may add additional stressors to the body, which may impact training strategies and should be considered when estimating the effort of performing aquatic exercise.