Simple SummaryA growing number of dogs and cats live together, sharing both a common home and common owner. Nevertheless, how do owners of both cats and dogs living in the same household perceive their pets’ personalities? We tried to answer this question by using a questionnaire targeted at people who owned both dogs and cats. Sociability, protectiveness, reactivity, neuroticism, and fearfulness were the traits that emerged and that diversified themselves according to species. Moreover, intrinsic animal factors, such as age and gender, demographic characteristics of the owner, and environmental context seem to modulate the perceived personality traits in a species-specific way. As personality might influence pets’ welfare and adaptability to the home environment, owners of multiple pets should know and take into consideration both common and differential aspects of their pet’s personality to optimise cohabitation among dogs and cats.AbstractThis study aims to define the personality traits perceived by the owners of multiple pets and to evaluate how they are modulated by experiential-environmental factors. A questionnaire was administered to 1270 owners of multiple pets (dogs and cats) to collect data on the demographics, management, and personality of their pets. Data were analysed by principal component analysis, bivariate, and multivariable models. Five personality traits emerged in dogs and cats: sociability, reactivity, protectiveness, neuroticism, and fearfulness. The owners perceived differences in the personality of their pet: dogs scored higher in sociability, protectiveness, and reactivity, while lower in the neuroticism dimension compared with cats (p < 0.001). Age similarly affected sociability (p < 0.01), and reactivity (p < 0.001) in both dogs and cats, while species-specific gender differences were found as to fearfulness (p < 0.05) and neuroticism (p < 0.001). The age of acquisition modulated several traits in dog personality, while living with conspecifics especially influenced cats. Physiological, behavioural, and evolutionary characteristics could explain species differences. Moreover, intrinsic and extrinsic factors modulated the five dimensions of dogs and cats in a diversified fashion, suggesting complex interactions between species and the environment. However, owners could have had different attitudes with their animals which could have influenced personality perception.