Astronium concinnum Schott ex Spreng. (Anacardiaceae) is a species used in civil construction, naval, luxury furniture, in addition to the potential for recovery and restoration of habitats. The objective of this work was to characterize the diversity and genetic structure of the A. concinnum in the Conservation Units, National Forest of Pacotuba and Private Natural Heritage Reserve of Cafundó, located in the south of the state of Espírito Santo. Eight ISSR primers were used, which produced 121 DNA fragments and 73.55% polymorphism. In the analysis of genetic dissimilarity, seven distinct groups were identified, with the majority of individuals (from both Conservation Units) being brought together into a single group. The genetic diversity of Nei (H*) and the Shannon index (I*), provided values for the species of 0.312 and 0.473, respectively, indicating the genetic diversity conserved in the species and its potential use for collecting genetically diversified seeds. The analysis of molecular variance revealed that most of the diversity (92.54%) is distributed within populations and the value of gene flow (Nm = 10.629) indicates the high rate of genetic exchange between Conservation Units. The results of the genetic structuring indicated the division of individuals into three genetic groups (K = 3), however, it was possible to observe a mixture of genetic material with the sharing of alleles between the three groups. The results indicate that A. concinnum trees maintain genetic diversity for their maintenance. In addition, the potential of the analysed individuals was certified as future matrixes for seed collection.