Context. Urban protected areas (PAs) are the habitat of several Neotropical medium-sized wild mammal (MSWM) species. However, this richness is seriously threatened by the growing populations of free-ranging dogs and cats in these areas.

Aims. The aim of the present study was to evaluate the effect of free-ranging dogs and cats on the assemblage structure of MSWM in PAs of Xalapa city, Veracruz, Mexico.

Methods. Camera traps were used to assess the effect of abundance and activity of dogs and cats on richness, abundance, dominance and activity of MSWM across two urban and three peri-urban PAs. The effect of plant diversity, vegetation structure and PA on mammal richness, activity and abundance were also evaluated.

Key results. The dominance of MSWM was higher in peri-urban areas than urban areas, and the activity of dogs and cats from peri-urban and urban PAs was similar with wildest MSWM. Only inside urban areas did the size of the area and the dogs’ activity have a negative effect on the richness, activity and abundance of MSWM. Moreover, the activity and abundance of cats also had a negative effect on the activity of MSWM in urban PAs. The presence of dogs affected the latency of appearance of MSWM.

Conclusions. The presence of free-ranging dogs and cats in urban PAs affects MSWM assemblages and their appearance latency.

Implications. The potential harm of free-ranging dogs and cats on the community of MSWM in urban areas is clear, as is the need for increased scientific research to aid in the control of these exotic species in urban landscapes.