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Ecoregions are regional-scale biodiversity units. Several of them converge in Salta Province, Argentina, where Puna and Monte are priority conservation areas for different reasons. The aims of our research were to (1) analyze the inventory obtained by determining the alpha and beta diversities of the arthropod communities in the ecoregions; (2) attempt to establish the most likely factors responsible for the distribution patterns of the epigeous communities present in the Monte and Puna take off; and (3) show the main changes in abundance and species richness of the most diverse arthropod groups recorded over space. Pitfall traps were used to collect epigeous arthropods. Several soil variables were measured in the field in addition to climatic variables. The total inventory and data by sites were evaluated using nonparametric estimators. Observed and estimated diversity values were used to compare epigeous arthropod communities between ecoregions. Beta diversity was assessed by different methods. The abundance-based Morisita index was used to investigate the degree of association between ecoregions and sampling sites. We used a non-metric multidimensional scaling analysis to show the ordination of the studied sites following the similarity of arthropod assemblages and possible relationships with environmental variables that could explain it. Species richness differed between ecoregions, and the true diversity showed that Puna was 1.30-times more diverse than Monte de Sierras y Bolsones. The inventory completeness was adequate (78%), and differed between sites. Species turnover was high with a clear ecoregional faunal separation. The most diverse arthropods orders were spiders, coleopterans, and hymenopterans, which exhibited differences in abundance and species richness between ecoregions. Different factors of soil heterogeneity and climate, which are important in arid environments, exerted an influence on the assemblages of epigeous arthropods obtained.