Linear infrastructures like roads, pipelines, and electrical networks are among the main causes of habitat fragmentation and diversity loss in animal species. We evaluated the effects of 20–30 m wide deforested corridors above underground oil pipelines on the movements of the long-furred woolly mouse opossum Marmosa paraguayana, an arboreal marsupial ubiquitous in the Brazilian Atlantic Forest. Using capture, mark, and recapture protocols along four transects, two on either side of the deforested corridor, one within the forest, and one along the forest edge, we compared movements within the forest with those across the deforested corridor. This experimental design was repeated in six locations within two protected areas in the state of Rio de Janeiro, Brazil. Pipeline crossings were rare, performed by few individuals, and significantly less frequent than movements inside the forest fragment, indicating that the deforested pipeline corridors act as a partial barrier to the move- ments of M. paraguayana. All crossings were restricted to the mating season. Both sexes crossed the pipeline strips and males travelled longer distances than females. Also, individuals used the forest interior more frequently and avoided edges, decreasing the likelihood of crossing the unfor- ested corridors. This study revealed an underestimated effect of a narrow-deforested matrix like the ones created by underground pipelines on forest connectivity and the need for the development of measures to mitigate these impacts.