The aim of this work was to evaluate the fl oristic composition, richness, and diversity of the upper and lower strata of a stretch of mixed rain forest near the city of Itaberá, in southeastern Brazil. We also investigated the diff erences between this conservation area and other stretches of mixed rain forest in southern and southeastern Brazil, as well as other nearby forest formations, in terms of their fl oristic relationships. For our survey of the upper stratum (diameter at breast height [DBH] ≥ 15 cm), we established 50 permanent plots of 10 × 20 m. Within each of those plots, we designated fi ve, randomly located, 1 × 1 m subplots, in order to survey the lower stratum (total height ≥ 30 cm and DBH < 15 cm). In the upper stratum, we sampled 1429 trees and shrubs, belonging to 134 species, 93 genera, and 47 families. In the lower stratum, we sampled 758 trees and shrubs, belonging to 93 species, 66 genera, and 39 families. In our fl oristic and phytosociological surveys, we recorded 177 species, belonging to 106 genera and 52 families. Th e Shannon Diversity Index was 4.12 and 3.5 for the upper and lower strata, respectively. Cluster analysis indicated that nearby forest formations had the strongest fl oristic infl uence on the study area, which was therefore distinct from other mixed rain forests in southern Brazil and in the Serra da Mantiqueira mountain range.