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In habitats with low water availability, a fundamental challenge for plants will be to maximize photosynthetic C-gain while minimizing transpirational water-loss. This trade-off between C-gain and water-loss can in part be achieved through the coordination of leaf-level photosynthetic and hydraulic traits. To test the relationship of photosynthetic C-gain and transpirational water-loss, we grew, under common growth conditions, 18 C 4 grasses adapted to habitats with different mean annual precipitation (MAP) and measured leaf-level structural and anatomical traits associated with mesophyll conductance (g m ) and leaf hydraulic conductance (K leaf ). The C 4 grasses adapted to lower MAP showed greater mesophyll surface area exposed to intercellular air spaces (S mes ) and adaxial stomatal density (SD ada ) which supported greater g m . These grasses also showed greater leaf thickness and vein-to-epidermis distance, which may lead to lower K leaf . Additionally, grasses with greater g m and lower K leaf also showed greater photosynthetic rates (A net ) and leaf-level water-use efficiency (WUE). In summary, we identify a suite of leaf-level traits that appear important for adaptation of C 4 grasses to habitats with low MAP and may be useful to identify C 4 species showing greater A net and WUE in drier conditions., (© 2020 John Wiley & Sons Ltd.)