Improving the welfare of companion cats requires that owners engage in responsible cat ownership practices. An important facet of understanding engagement in responsible cat ownership behaviors involves identifying the psychosocial processes that predict whether cat owners engage, or fail to engage, in responsible cat ownership behaviors. The aim of this study was to use the Theory of Planned Behavior (TPB) as a conceptual framework to understand engagement in responsible cat ownership practices such as de-sexing, paying for the care of cats, and containment of cats. An online questionnaire was completed by 274 Singaporean cat owners to investigate the relationship between the constructs of the TPB (attitudes, subjective norms, perceived behavioral control, and intentions) and actual engagement in responsible cat ownership behaviors. With only one exception, all respondents indicated having engaged in at least one responsible cat ownership practice. Forward stepwise binary logistic regression analyses revealed that responsible cat ownership behaviors were predicted by demographic and TPB variables. Cat de-sexing was predicted by attitudes and perceived behavioral control, while paying for the care of a cat was predicted by employment status and perceived behavioral control. Cat containment practices were predicted by gender, attitudes, subjective norms, and perceived behavioral control. These findings may be used to develop targeted educational programs to promote engagement in responsible cat ownership behaviors.