Based on exhaustive studies of herbarium specimens held at the National Herbarium of Mexico (MEXU), as well as of the literature, an updated list of the native species of trees of the Mexican portion of the Yucatan Peninsula is provided (Campeche, Quintana Roo y Yucatan). For each species the state(s) in which it occurs is cited. The list includes 437 species belonging to 246 genera and 68 families. An appendix listing 376 excluded species, including 68 of dubious occurrence in the peninsula is provided, clarifying the reason for their exclusion as members of the flora of the Peninsula. The richest families are Mimosaceae, Euphorbiaceae, Fabaceae, Rubiaceae, and Myrtaceae; the richest genera are Acacia, Eugenia, Coccoloba, Croton and Lonchocarpus. The percentage of endemism is around 12.3% (54 taxa in 26 families); the families with more endemic species are Cactaceae, Fabaceae, Mimosaceae, Polygonaceae and Rubiaceae. At the state level, Quintana Roo harbors the most species (351). The use of five different similarity coefficients (Braun-Blanquet, Dice, Drive & Kroeber, Jaccard and Simpson) to analyze both the total number of species and the endemic ones, supports the idea of considering the states as part of the same floristic province. Finally, the need to intensify the floristic and taxonomic work, aimed at evaluating in the near future more properly the floristic richness in the Peninsula is pointed out. This will allow a more precise definition of its floristic subdivisions, its degree of endemism and its floristic relationships with neighbouring regions.