Oak-dominated forest has declined in the eastern United States as shade-tolerant mesophytic species (e.g., maple [Acer spp.]) replace oaks (Quercus spp.), sparking concern among ecologists regarding species that consume acorns. Our goal was to describe how increasing mesophication of oak forests may affect consumers in higher trophic levels. We investigated relationships among forest composition, mast production, small-mammal density, and carnivore occurrence in 8 stands representing a gradient of oak–hickory dominance in central hardwood forest in southern Illinois. We livetrapped small mammals for >24,000 trap-nights in June–August 2009–2011 with trapping webs to estimate population density of mice (Peromyscus spp.). We collected mast seeds during October–November 2009–2010 and calculated average dry biomass (g/m²) for each species and stand. During winters 2009–2011, we photographed carnivores using baited camera traps. We regressed mast biomass on measures of forest composition and regressed Peromyscus density and carnivore occurrence on estimates of mast biomass. Peromyscus summer density was not related to percent hard-mast basal area or hard-mast biomass from the previous autumn. Logistic regressions of carnivore occurrence on Peromyscus density were not significant. Many other studies have demonstrated links of several species to oak forest and mast production, but the lack of associations that we observed was consistent with recent meta-analyses across latitude. The landscape matrix of oak–hickory forest and alternative soft-mast foods also may act to homogenize Peromyscus density across our study sites. Maintenance of stand heterogeneity in the forest landscape will support a wider diversity of species.