Accumulating evidence from studies of human-animal interaction highlights the physiological, psychological, and social benefits for older owners of dogs and cats. This longitudinal study examined whether experience of dog/cat ownership protects against incident frailty in a population of community-dwelling older Japanese. Among 7881 non-frail community-dwelling adults aged 65 years or older who completed a mail survey in 2016, 6,197 (mean [SD] age, 73.6 [5.3] years; 53.6% women) were reevaluated in a 2018 follow-up survey. Frailty was assessed with the Kaigo-Yobo Checklist. Incident frailty was defined as a score of four or higher in the follow-up survey. Overall, 870 (14.0%) were current dog/cat owners, 1878 (30.3%) were past owners and 3449 (55.7%) were never owners. During the 2-year follow-up period, 918 (14.8%) developed incident frailty. Mixed-effects logistic regression models showed that the odds ratio for incident frailty among dog/cat owners, as compared with never owners, current owners were 0.87 (95% confidence interval [CI]: 0.69-1.09) and past owner were 0.84 (0.71-0.98), after controlling for important confounders at baseline. In stratified analysis, the risk of incident frailty was lower for past dog owners than for cat owners. Longer experience of caring for a dog requires physical activity and increases time outdoors spent dog walking and thus may have an important role in maintaining physical and social function and reducing frailty risk among older adults.