We use the CERES family of crop models to assess the effect of different spatial scales of climate change scenarios on the simulated yield changes of maize (Zea mays L.), winter wheat (Triticum aestivum L.), and rice (Oryza sativa L.) in the Southeastern United States. The climate change scenarios were produced with a high resolution regional climate model and a coarse resolution general circulation model, which provided the initial and boundary conditions for the regional model. When considering the effect of the climate change only at the individual state level, maize yields decreased in all states for both scenarios (-5 to -29%), but the differences in yields between the two scenarios were generally significant, the coarse scale showing the larger decreases. Winter wheat yield decreases (-27 to -48%) were larger than those for maize but the differences in yields produced by the two climate change scenarios were insignificant in most states. With elevated CO₂ for maize the signs of yield changes differed between the two scenarios. For maize and winter wheat, the primary climate variable that explained the contrast in the yields calculated from the two scenarios is the precipitation during grain fill leading to different water stress levels. Temperature during vernalization explains some contrasts in winter wheat yields. Scenario scale resulted in significantly different rice yields, but mainly because of low variability in yields. With adaptation, the contrasts in the yields of all crops produced by the scenarios were reduced but not entirely removed. Our results suggest that spatial resolution of climate change scenarios can be an important uncertainty in climate change impact assessments.