In an investigation of perceptions of the conflicts between people and jaguars on the Amazon deforestation frontier and Pantanal, Brazil, we explored how perceptions of the impact of jaguars on livestock and on human safety vary with experience of jaguars (including reported livestock loss), region, place of residence, attitudes towards jaguars, knowledge of the species, and perceptions of changes in jaguar abundance and the regional economic situation. Livestock loss and threat to human safety were not the only predictors of the perceived conflict with jaguars. Livestock loss acted in combination with attitudes, knowledge and perceptions of the economic situation to determine how people perceive the impact jaguars have on their livelihoods. Attitudes and knowledge were influenced by age, gender and whether respondents lived in urban or rural areas. An experiment in which respondents were shown photographs of dead livestock, and asked to ascribe the cause of death, revealed an interaction between attitudes and knowledge: of respondents whose knowledge of the species was low, those with negative attitudes towards jaguars assigned a larger number of photographs to jaguar depredation. Our evidence suggests that attitudes and knowledge can affect the conclusions a rancher draws from finding the carcass of a cow, or even from noticing that a cow is missing. The owners of smaller holdings believed that depredation was more serious on neighboring properties than on their own, which suggests that their perceptions of conflict with jaguars were shaped primarily by what is heard from other people, and not by personal experience.