The State of Guerrero, Mexico, has priority marine areas for conservation of its biodiversity, but information concerning diversity of mollusks is limited, so it is convenient to carry out species inventories, studies of populations and community ecology. This study was conducted in the intertidal rocky beach Tlacopanocha. The objectives were to determine richness, density and species diversity, analyze the species composition and size structure. The sampling area was 10 m(2) and the sampling unit was 1 m(2). 35 species were identified of which three are new records for the intertidal rocky shores of the State of Guerrero. The best represented families in species richness were Ischnochitonidae and Arcidae, and Chamidae, and Chitonidae in abundance; species density was 31.60 ind m(-2). Polyplacophora showed 42.9% of dominant species and Bivalvia 19.0%. Chama corallina showed the greatest length and Chama sordida the greatest width. Species richness of mollusks recorded is considered high and in agreement with tropical rocky substrates. Polyplacophora showed high species composition, which could be the result of adaptation of organisms to the dynamic conditions of the rocky intertidal. New records indicate the importance of species inventories and knowledge of the populations and community's dynamics of the Guerrero marine fauna.