The coexistence of sympatric species is determined by differences in their ecological niche. Thus, for taxonomically and ecologically similar species to coexist, they must segregate in at least one of the three most important dimensions of the ecological niche: space, time or diet. The Pampas Cat Leopardus colocola and the Sechuran Fox Lycalopex sechurae are sympatric species; and they are the most common medium-sized carnivores in the Sechura Desert and in the lowland seasonally dry tropical forest of Peru and Ecuador. We evaluated the activity pattern of both mesocarnivores using camera trapping and temporal overlap analysis in both arid ecosystems. We found a high degree of activity overlap and no statistically significant difference in the activity pattern of both species (Δ = 0.85 with 95% CI = 0.81-0.94; W = 0.531, SD = 2, P = 0.767), both being cathemeral. There is, however, a contrasting pattern in the daytime activity of these species in the dry forest. These results suggest that the different diet composition may be the main dimension that is facilitating the coexistence of both mesocarnivores in the arid ecosystems of northern Peru and southern Ecuador.