<p>Generalist mesocarnivores inhabiting peri-urban landscapes are expected to adjust their diet to exploit the high availability of invasive prey species that thrive in these environments. However, long-term assessments are needed to understand how carnivores respond to changes in prey composition driven by peri-urban expansion and intensification. We assessed two-decade changes in the diet of the South American gray fox (<i>Lycalopex griseus</i>) a peri-urban landscape of southern Chile. Specifically, we tested whether gray foxes have shifted from a diet primarily based on native rodents to one dominated by invasive prey in response to temporal changes in habitat conditions. Scat surveys were conducted in 2003 and 2023 across 30 plots comprising native forests and forest plantations. Logistic regression and Bayesian hierarchical models were used to assess temporal changes and habitat effects on prey consumption. The probability of consumption of native mice, total native rodents, and European rabbits decreased over time, whereas consumption of invasive rats (<i>Rattus</i> spp.) and European hares increased. The relative consumption of rats and European hares increased by more than threefold and twofold, respectively. Native rodents were more frequently consumed in native forests than in forest plantations. The effects of habitat variables on the consumption of European hares and native mice exhibited temporal variability. Overall, the observed dietary shit in gray fox’s is likely associated with changes in habitat conditions. However, ongoing loss of native forests introduces uncertainty regarding future dietary trajectories.</p>