AIMS/INTRODUCTION: A low level of urine pH (U-pH) has been reported to be associated with metabolic disorders. However, the relationship between the incidence of diabetes mellitus and U-pH has not yet been fully addressed. MATERIALS AND METHODS: We investigated the relationship between U-pH and the development of diabetes mellitus during a 10-year period in a general population of individuals who received annual health examinations in 2006 (n = 28,990). After exclusion of individuals with missing data, and those with diabetes mellitus and/or chronic kidney disease at baseline, a total of 12,476 individuals (men/women: 8,027/4,449) who received health examinations at least once during the period from 2007 to 2016 were recruited. The recruited individuals were divided into four groups according to their U-pH levels: groups of U-pH ≤5.0, 5.5, 6.0 and ≥6.5. RESULTS: During a 10-year period, 521 men (6.5%) and 132 women (3.0%) had new onset of diabetes mellitus. The cumulative incidence of diabetes mellitus was 7.5% (men/women: 9.3%/4.4%) per 100 person-years. The hazard ratios (HRs) in the U-pH ≤5.0 (HR 1.93) and U-pH 5.5 groups (HR 1.46) were significantly higher than that in the U-pH ≥6.5 group as a reference for men, but not for women. After adjustment of age, obesity, fasting glucose, smoking and alcohol drinking habits, family history of diabetes mellitus, and use of drugs for hypertension and dyslipidemia, HR in the U-pH ≤5.0 group (HR 1.39) was significantly higher than that in the U-pH ≥6.5 group for men, but not for women. CONCLUSIONS: Low U-pH predicts new onset of diabetes mellitus in a general population of men.