Jaguars Panthera onca coexist with pumas Puma concolor across their entire range. In areas where they occur together their coexistence may be facilitated by differences in diet. This study compared food habits of jaguars and pumas in Belize, Central America, across a protected lowland rainforest and the neighbouring human-influenced landscape. Diets were determined from 362 jaguar scats and 135 puma scats, identified by genetic analysis. In the protected forest, dietary breadths were low for jaguars and pumas and showed little overlap. In this habitat each relied heavily on a single medium-sized (5–10 kg) prey species: armadillos Dasypus novemcinctus for jaguars, and pacas Agouti paca for pumas. Both cats also took larger prey (>10 kg), mainly white-lipped peccaries Tayassu pecari by jaguars and red brocket deer Mazama americana by pumas. In unprotected fragmented lands, jaguar scats rarely contained large wild prey species; rather, a diet of relatively small wild prey was supplemented with larger domestic species. Pumas did not take domestic species and were scarce outside the protected forest, possibly indicating competition with humans for pacas and deer, which are also prized game species in the region. This study is the largest analysis to date of sympatric jaguar and puma diets in both forest and farmland. We suggest that jaguar predation on cattle may be reduced by ensuring that game hunting is sustainable and potentially by augmenting forests within the human matrix with large wild ungulates. The supplementation could benefit both of the cat species, and the local game hunting economy.