Renal dysfunction is reported to be associated with poor outcomes in patients with chronic heart failure (CHF). A recent study showed that acidic urine is related to chronic kidney disease, which is a risk factor for the development of CHF. However, it remains to be determined whether acidic urine is associated with poor outcomes in patients with CHF. We measured urine pH using dipsticks in 537 patients with CHF. Acidic urine was defined as urine pH ≤5.5. Patients were prospectively followed during a median follow-up period of 556 days. There were 145 cardiac events. Prevalence of acidic urine was increased with advancing stage of chronic kidney disease. Patients with acidic urine had a more severe New York Heart Association functional class compared with those with normal urine. In the multivariate Cox proportional hazard analysis, acidic urine was independently associated with poor outcomes in patients with CHF after adjustment of confounding factors. A Kaplan–Meier analysis demonstrated that the rate of cardiac events was higher in patients with acidic urine than in those with normal urine. The presence of acidic urine can reliably identify patients at high risk of future cardiac events in patients with CHF.