We investigated species composition and diversity parameters of beetle communities in two planted saxaul ( Haloxylon ammodendron , black saxaul) forests in Southern Mongolia. We also studied nearby natural areas for comparison. Beetles were mainly collected by pitfall traps. 1064 individuals of 38 species of 22 genera in 4 beetle families were identified from planted plots. In comparison, a total of 1395 beetles belonging to 40 species of 24 genera in seven families were collected and identified from the natural saxaul plots. The most diverse beetle families were darkling beetles ( Tenebrionidae , 18 species) and snout beetles ( Curculionidae , 15 species) in planted and natural saxaul plots. We recorded several species ( Apatophysis serricornis , Cephogenia chinensis , and Eumylada punctifera punctifera ) which are associated with the saxaul tree. A darkling beetle, Anatolica potanini , was the dominant species in both natural and planted plots of the Nariin Zag forest. There were significant differences in the species richness and abundance between the planted and natural plots of the Ukhaa Zag forest. It is possible that the age of the plantation drove the differences. The higher values of diversity indices and species richness in the planted plots can be explained by the presence of rare species, represented by only one or two individuals. The planted plots and corresponding natural plots within each forest were more similar to each other in species composition and abundance than between forests.