Information on genetic diversity from one generation to its next generation is an important factor for management and conservation in a seed orchard. The purpose of this study was to evaluate the level of genetic diversity of parental as the first generation (F1) and offspring (F2) of Acacia mangium in the A. mangium seed orchard Group D (AM004) in South Sumatera. Analysis was conducted on 251 parental trees and ± 200 seeds from 10 mother trees. Analysis using 12 microsatellite markers showed that mean number of detected allele (A) for all the parents and offspring was 8.23 and 7.08, repectively. In general, the level of genetic diversity in parental and its offspring was not different (He=0.609 for parental and He=0.606 for offspring). The presence of new alleles that was detected from offspring indicated the possibility of pollen contamination from outside the seed orchard.