This study investigated the effect of feeding synthetic Zeolite A (sodium aluminum silicate) prepartum on blood minerals, metabolic indices, milk production, and reproduction in grazing dairy cows. Multiparous Holstein-Friesian cows were randomly allocated to either an untreated control group (n = 23) or a treatment group receiving 500 g/cow/d Zeolite A (n = 24) for 14 d before expected calving date (actual duration = 19.2 ± 3.9 d prepartum). Cows grazed pasture and were individually supplemented with 2–3 kg DM/cow/d maize silage with or without zeolite prepartum. Pastures were dusted with 90 g/cow/d magnesium oxide throughout and cows received 200 g/cow/d calcium carbonate for 4 d postpartum. Blood samples were collected pre-treatment (d −19) and at d-14, 0, +1, +2, +3, +4, +7, +14, +21, and +28 relative to calving. A subset of cows (n = 10 per group) also had blood collected daily from d −10 to +10, and again at d +18 and +24. Data were analyzed using a repeated-measures ANOVA with a mixed model (Proc Mixed, SAS 9.3) including treatment, day, and their interaction as fixed effects, cow as a random effect, and treatment duration and pre-treatment data as co-variants. Zeolite increased (P < 0.05) plasma calcium concentrations compared with controls from d −1 to +4 relative to calving; reducing the average prevalence of subclinical and clinical hypocalcemia (<2 and < 1.4 mmol/L plasma calcium) from 22.6 and 2.6% to 0% (P < 0.001 and P = 0.07), respectively. Plasma phosphorus were lower between d −14 to −1 prepartum (P < 0.001) and on d 0 and +1 (P < 0.001) and d +2 (P = 0.09) postpartum, indicating hypophosphatemia. Zeolite-treated cows also had lower (P < 0.05) average plasma magnesium prepartum, particularly on d −1 and 0. There were no differences (P ≥ 0.35) in milk yield, energy-corrected milk yield, or somatic cell count during the first 100 d in milk. Plasma β-hydroxybutyrate and nonesterified fatty acid concentrations, and BW and BCS did not differ between groups (P ≥ 0.39). Zeolite cows calved 2.8 d earlier (SED 1.04; P < 0.05) than control cows and conceived 7.5 and 13.8 d earlier (P = 0.09) relative to calving and the start of seasonal mating, respectively. In conclusion, prepartum Zeolite A supplementation in grazing cows reduced hypocalcemia risk and tended to reduce days to conception, but did not alter milk production or indicators of metabolic status.