In mature ruminants, B vitamins are produced by rumen microbes but the newborn calf relies on placental and colostral transfer of the vitamins to cover its requirements. The study was conducted to evaluate biotin (B8), folates (B9) and vitamin B₁₂ (B12) concentrations in colostrum of cows receiving vitamin supplements and in plasma of their calves fed with their colostrum. Dietary B8 supplement (0 or 20 mg/d) and dietary B9 supplement (0 or 2.6 g/d) + weekly intramuscular injections of B12 (0 or 10 mg) were used in a 2 × 2 factorial arrangement. Cows (n = 34) received one of the 4 treatments from −26 (SD 8) to 0 relative to the parturition. Cows were blood sampled once the week before calving. Colostrum was harvested at first milking from all cows. Calves were fed 2.4 (SE 0.3) kg of their dam colostrum with a nipple bottle within 3 (SD 2) h of birth. Any calf born as twin or not receiving their dam colostrum were excluded; 23 calves were blood sampled and weighed 25 (SD 4) h after birth (B8-B9B12- n = 4; B8+B9B12- n = 7; B8-B9B12+ n = 6; B8+B9B12+ n = 6). Data (log-transformed when needed) were analyzed using Proc MIXED of SAS. In dams, supplementary B vitamins increased their respective plasma concentrations (P ≤ 0.01). Colostral and calf plasma IgG concentrations did not differ among treatments (P ≥ 0.14). The B8 supplement increased colostrum B8 from 35 to 298 ± 23 ng/mL and calf plasma B8 from 1.0 (95% confidence interval (CI):0.8–1.2) to 8.1 (CI:6.7–9.7) ng/mL (P < 0.01). Supplementary B9B12 increased colostrum B9, from 673 to 1,094 ± 52 ng/mL, colostrum B12, from 29 to 58 ± 3 ng/mL, calf plasma B9 from 16 to 30 ± 2 ng/mL (P < 0.01) and tended to increase (P = 0.09) calf plasma B12 from 0.8 (CI:0.5–1.1) to 1.2 (CI:0.9–1.7) ng/mL (P < 0.01). Calves born from dams receiving the B9B12 supplement were heavier (50 vs. 44 ± 1 kg; P < 0.01); B8 supplement did not affect calf weight (P ≥ 0.6). Further studies are needed to evaluate if the increase in calf birth weight when a B9B12 supplement was given to cows in late gestation could be due to an epigenetic effect as reported for other species.