Cardiac output (Q) and tissue blood flows (BF) were measured in four ponies at rest, after 30 min of moderate exercise (ME) (∼30% V̇O2max) and following moderately intense exercise (M-IE) (∼65%) until fatigue, in a mildly hot (MH) environment (dry bulb temperature = 41°C, wet bulb temperature = 27.5°C). Exercise at both intensities resulted in increases in Q (15.6 ± 1.7 [rest] vs. 35.8 ± 2.6 [ME] vs. 48.6 ± 3.9 [M-IE] l/min) and V̇O2 (4.7 ± 0.9 vs. 24.5 ± 1.2 vs. 55.8 ± 5.8 ml/kg/min). When compared to ME, M-IE resulted in decreases in BF to the skin (∼15%), nonworking muscle (46%), fat (93%), gut (56%), kidneys (57%), CNS (31–66%) and an increase in BF to respiratory (68%), limb (98.5%) and cardiac (50%) muscles. In contrast, BF to working muscle during ME in thermoneutral (TN) conditions (McConaghy et al. 2002) was higher than found during ME in MH. We calculated that limb BF was ∼25% lower for ME in MH vs. ME in TN. Similarly, we estimated that limb BF during M-IE in MH was ∼25% lower than for M-IE in TN. Attenuation of the increases in muscle BF during exercise in the heat may be a determinant of the onset of fatigue.