Polyhalite is a hydrated sulfate of potassium, calcium and magnesium. Based on its anionic properties, we hypothesized that feeding polyhalite mineral would decrease urine pH when fed to nonlactating cows before calving. The objective of this study was to determine if the mineral polyhalite is an effective means to decrease urine pH when fed to pre-partum dairy cows. At 21 d before expected calving date (ECD), 45 Holstein and Jersey dairy cows were transferred from the far-off to the close-up nonlactating groups, respectively. Close-up cows were housed in a common pen bedded with wood shavings, and they were fed a common diet that contained (DM basis) 48% corn silage, 25% grass hay, and 27% concentrate and 14.4% CP, 44.7% NDF, and 32.1% NFC concentrations. The granular free-flowing anionic test product was provided in the pelleted concentrate and included in the diet at a rate equal to 3.9% DM (i.e., ~500 g/day), yielding an estimated DCAD of −20 mEq/100 g DM. On d 21, 14, 7, and 0 relative to ECD, urine samples were collected, and urine pH was immediately determined with a portable pH meter. Urinary pH was statistically evaluated as repeated measures using the MIXED procedure of SAS. For this analysis, cow was considered the experimental unit from which the effect of time since feeding polyhalite on urine pH was evaluated using repeated measures. The model included the random effect of cow (44 df), the fixed effect of day (3 df), and the random residual error. Feeding a close-up diet containing ~500 g/d of polyhalite mineral significantly reduced urine pH of nonlactating dairy cows (P < 0.01). Urine pH of the far-off cows at 21 d before ECD was 8.26, while urine pH of the close-up cows at 14, 7, and 0 d relative to ECD were 5.18, 5.12, and 5.15, respectively. In conclusion, feeding ~500 g/day of polyhalite mineral in close-up diets is an effective means to decrease urine pH when fed to pre-partum dairy cows.