Abstract Cellulose and beet pulp have been commonly used in the pet food industry to increase the dietary fiber content of cat foods. However, pet food companies seek alternatives to these so-called byproducts. Miscanthus grass is grown for its fiber content and may serve as an alternative to traditional fibrous ingredients. The objectives of this study were to determine the effects of fiber sources on extrusion processing and kibble structure of cat foods. Three replicate batches of a complete and balanced foods for adult cats at maintenance each containing 10% of Miscanthus grass, cellulose, or beet pulp was mixed and kibbles were produced on a single-screw extruder. Feed rate, preconditioner water and steam, extruder screw speed, extruder water and steam addition, and knife speed were adjusted to achieve a wet bulk density of 330 g/L. After extrusion, kibbles were dried at 115.5 ºC to less than 10% moisture. Dried kibbles were coated with chicken fat and flavor enhancer. No effects due to fiber source were reported for extrusion parameters or kibble measurements (P > 0.05) with the exception of compression energy, wherein kibbles produced with cellulose required more energy to compress than those containing beet pulp (6,917 N mm vs. 3,591 N mm, respectively). In conclusion, tested fiber sources had no impact on extrusion parameters and most kibble characteristics. Kibbles containing cellulose required more energy to compress than kibbles containing beet pulp. Miscanthus grass could be used as an alternative to traditional fiber sources used to produce cat foods.