BACKGROUND: Although respiratory rate has been a sensitive predictor for prognosis in acute settings, resting respiratory rate (RRR) is undervalued in chronic care. The clinical significance of RRR among older people is not well documented. AIM: We investigated the association between RRR and all-cause mortality among older outpatients. METHODS: A retrospective cohort study exhaustively included patients who had undergone medical checkups in a facility between April 2017 and March 2018 and followed up for at least 2 years. We excluded patients who were less than 60 years of age or had not undergone regular outpatient appointments. Sex, age, smoking habits, history of hospitalization, polypharmacy, long-term care insurance certification status, Mazzaglia index, pulse rate, systolic blood pressure, and Charlson Comorbidity Index were measured at the baseline medical checkup. Survival was confirmed by chart review and by contacting physicians in charge. The risk ratios were estimated by converting the odds ratios derived from the multivariable logistic regression models. RESULTS: Of the 853 patients who underwent baseline checkups, 749 were enrolled in the analyses; death occurred in 53 patients (7.1%), with no loss to follow-up. The RRR was independently associated with all-cause mortality after adjusting for covariates [adjusted risk ratio of RRR per 1 bpm = 1.14, 95% confidence interval (CI): 1.06 - 1.22]. DISCUSSION: Given the independent association of RRR for existing predictors, this simple index seems worthy of consideration in further studies aimed at defining its predictive role in older people and in different settings. CONCLUSION: RRR was independently associated with all-cause mortality.