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Amazon rainforest is facing several threats due to anthropogenic activities causing loss of habitat, species, and ecosystem functions. However, several areas are being abandoned after anthropic use allowing secondary succession to occur, which can lead to the passive restoration of community parameters that have been lost. We aimed to investigate the effects of vegetation structure on dung beetle assemblages along a successional gradient in the western Amazon rainforest. Dung beetles were sampled and forest structure variables were measured using standardized protocols along primary, late secondary, and early secondary forests. We used a combination of generalized linear models and multivariate analyses to test for differences in assemblage composition and structure among successional stages and their relationships with vegetation variables. We found that primary forests have different species compositions from both late and early successional forests, with several species strongly associated with primary forests. Dung beetle abundance was higher in primary forests and influenced by variables describing the successional stages (i.e., tree density). Species turnover was the most important beta-diversity component among and within each successional stage, with lower values in early secondary forests. Different pathways followed by secondary forests during forest succession may lead to increased species turnover similar to that found in primary forests. Biodiversity conservation will only work if secondary forests are allowed to recover to a late successional stage close to a primary forest stage. The loss of primary forests can cause an irreversible loss of species in need of conservation and with great functional importance in the Amazon rainforest.