Objectives The aim of this study was to compare the carbohydrate content of grain-containing and grain-free dry cat diets and compare major protein and carbohydrate sources of these diets. Methods This was a cross-sectional study of 77 randomly selected dry cat diets (42 grain-containing, 35 grain-free). Reported carbohydrate values were compared between grain-containing and grain-free cat diets. A subset of 25% of diets from each category (grain-containing and grain-free) was analyzed and nitrogen-free extract was calculated as an estimate of carbohydrate content. These calculated values were compared with reported values from the manufacturer. Animal- and plant-sourced ingredients were also compared between grain-containing and grain-free diets. Results Mean reported carbohydrate content of the grain-free diets (n = 35) was lower than the grain-containing diets (n = 41; 64 ± 16 vs 86 ± 22 g/1000 kcal; P <0.001). Reported carbohydrate values were higher than analyzed nitrogen-free extract (n = 20; 79 ± 30 vs 73 ± 27 g/1000 kcal; P = 0.024). Poultry ( P = 0.009) and soy (P = 0.007) were less common in grain-free diets than in diets containing grain. The alternative carbohydrate sources of chickpeas, lentils, peas, potato, sweet potato and cassava/tapioca were more common ( P <0.05) in grain-free diets than in diets containing grain. Conclusions and relevance This sample of grain-free diets had lower mean reported carbohydrate content than grain-containing diets, but there was considerable overlap between groups and individual diets' carbohydrate/nitrogen-free extract content varied widely.