Polyhalite is a natural mineral that could be fed as an acidogenic product to induce metabolic acidosis and prevent hypocalcemia in dairy cows after calving. The objectives were to determine if feeding polyhalite is an effective means of reducing urine pH and if feeding polyhalite negatively affects dry matter intake during the prepartum period. Twenty-four nonlactating and pregnant Holstein cows entering their second or greater lactation were fed one of 4 experimental close-up diets. The experimental diets included (DM basis) 48% corn silage, 25% grass hay, and 27% of 1 of 4 pelleted concentrates, which provided: 1) no acidogenic product (CON), 2) 200 g/day of polyhalite (LOW), 3) 400 g/day of polyhalite (HIGH), and 4) 250 g/day of calcium chloride (CHL). At 21 d before their expected calving date (ECD), cows were transferred from the far-off to the close-up group. While in the close-up group, cows were fed individually using a Calan gate feeding system. Dry matter intake was measured individually on a daily basis. On d −21, −14, −7, and 0 relative to ECD, urine samples were collected after vulva stimulation in the morning before feeding. Urine pH was determined immediately after collection using a portable pH meter. Data were analyzed with Proc MIXED of SAS. The statistical model included the fixed effects of diet, day, and diet by day and the random effects of block and block by diet. Both variables were tested using the autoregressive covariance structure for repeated measures (cow = subject). Urine pH differed among diets (P < 0.01). Cows consuming CON and LOW had the highest urine pH (8.06 and 8.02, respectively), and cows consuming HIGH and CHL had the lowest urine pH (6.35 and 6.70, respectively). Dry matter intake did not differ among diets (13.7 kg DM/d; P > 0.83) but decreased toward calving (P < 0.01). Dry matter intake toward calving decreased similarly for all diets (P > 0.76). In conclusion, feeding polyhalite is an effective means for inducing metabolic acidosis without reducing dry matter intake. Based on these results, polyhalite should be fed at a dose of 400 g or more per cow per day to reduce urine pH.