Ecological corridors are essential for maintaining ecosystem functionality, as they facilitate the movement of species between protected areas. In the Central Italian Apennines, five corridors have been identified to enhance habitat connectivity for the critically endangered Marsican brown bear (Ursus arctos marsicanus). This study focuses on two of these corridors to investigate their support of other mammal species populations. We collected data from camera traps over four months, and applied a Random Encounter Model to estimate the population densities of eight meso- and macro-mammal species. We compared the densities we estimated with those reported in the literature for different locations across Europe. The results indicated higher-than-average densities for several species compared to published data, especially for ungulates. These findings underscore the broader importance of Marsican bear corridors, providing important habitats for several mammal species. This type of analysis can be replicated in the same area at different times, or in other coexistence corridors for large carnivores, to support management strategies. Effective management of these corridors, with a focus on reducing human disturbance and improving habitat connectivity, will be critical for the long-term survival of both the Marsican bear and its coexisting species.