Co-products from the ethanol industry, such as distillers dried grains with solubles (DDGS), can provide alternative protein sources for pet food. Corn fermented protein (CFP) is produced using post-fermentation technology to split the protein and yeast from fiber prior to drying. This results in a higher protein ingredient compared to DDGS, increasing its appeal for pet food. In addition, the substantial yeast component, at approximately 20-25%, may promote gut health through modulation of the microbiome and the production of short chain fatty acids. Therefore, the objective of this study was to determine the effect of CFP on the fecal microbiome of cats. The four experimental diets included a control with no yeast (T1) and diets containing either 3.5% brewer's dried yeast (T2), 2.5% brewer's dried yeast plus 17.5% DDGS (T3), or 17.5% CFP (T4). All diets except T1 were formulated to contain 3.5% yeast. Diets were fed to adult cats (n = 11) in an incomplete 4 x 4 replicated Latin square design. Cats were adapted to diet for 9 days followed by a 5-d total fecal collection. During each collection period, fresh fecal samples from each cat were collected and stored at -80°C until analysis. Fresh fecal samples (n = 44) were analyzed by 16S rRNA gene sequencing. Raw sequences were processed through Mothur (v.1.44.1). Community diversity was evaluated in R (v4.0.3, R Core Team, 2019). Relative abundance was analyzed within the 50 most abundant operational taxonomic units (OTU) using a mixed model of SAS (v9.4, SAS Institute, Inc., Cary, NC). Diet was the fixed effect and cat and period were random effects. Results were considered significant at P < 0.05. Alpha-diversity indices (Observed, Chao1, Shannon, Simpson) and beta-diversity metric (principal coordinate analysis) were similar for all treatments. Predominant phyla were Firmicutes (66%), Bacteroidetes (25%), Actinobacteria (8%), Proteobacteria (0.64%), and Desulfobacteria (0.54%). The relative abundance of Firmicutes and Actinobacteria was lower (P < 0.05) for T3 compared to T4 and T2, respectively. On a more specific phylogenic level, 17 genera resulted in differences (P < 0.05) among dietary treatments. Overall, this data indicates that compared to traditional yeast and distillers dried grains, CFP did not alter the overall diversity of the fecal microbiome of healthy adult cats over a 14-d period.