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With average global temperatures predicted to increase over the next century, it is important to understand the extent and mechanisms of C₄ photosynthetic acclimation to modest increases in growth temperature. To this end, we compared the photosynthetic responses of two C₄ grasses (Panicum coloratum and Cenchrus ciliaris) and one C₄ dicot (Flaveria bidentis) to growth at moderate (25/20 °C, day/night) or high (35/30 °C, day/night) temperatures. In all three C₄ species, CO₂ assimilation rates (A) underwent significant thermal acclimation, such that when compared at growth temperatures, A increased less than what would be expected given the strong response of A to short‐term changes in leaf temperature. Thermal photosynthetic acclimation was further manifested by an increase in the temperature optima of A, and a decrease in leaf nitrogen content and leaf mass per area in the high‐ relative to the …