Resumo. This study aimed to characterize the floristic composition and structure of mangroves in three municipalities in Pará, to identify possible conservation and environmental change indicators. At each site, three plots were delimited in 10 x 50 m, registering the species present and measuring DAP and height. Were analized density, frequency and dominance, hedge value index and importance. Typical species found were Rhizophora mangle L., Rhizophora racemosa G.F.W. Meyer, Avicennia germinans (L.) Stearn. e Laguncularia racemosa (L.) Gaertn. Rhizophora racemosa found only in Soure and Laguncularia racemosa only in Salinópolis. The Soure of forest had higher mean values of height and diameter and, in the three areas, Avicennia germinans showed the highest values of height and diameter. The largest basal area values for living individuals occurred in Soure and Salinas, and dead individuals, the greatest contribution was in Maracanã, both for the class > 10.0 cm DBH. In Soure were not recorded dead individuals. The woods had a high degree of structural development and are adjusted to the pattern found in Brazil’s northern coast. Joint information about the floristic composition, abundance, density and parameters that show the degree of structure thereof other than registration and analysis of dead individuals, are good indicators of this ecosystem conservation status. Concluded at good state of conservation of mangroves in this region. However, preventive actions management and conservation are essential to ensure the maintenance of its resources.