Weaning involves upregulation of rumen function and B-vitamin (B-vit) supplementation has been considered unnecessary due to their production by rumen microbes. Literature data are equivocal concerning the need for supplemental dietary B-vit through the transition phase. The hypothesis was that B-vit are limiting during the transition period and to be effective, the vitamins must be fed in a protected form. To evaluate the effect of supplementing B-vitamins on calf performance, sixty-one 3-week-old Holstein calves were individually housed from birth to 13 wk of age. Milk replacer (MR; 28% CP, 15% fat) was offered up to 1.6 kg DM/d at 15% solids, 3 times/d. Starter grain (SG; 25.5% CP, 2.5 Mcal ME/kg) with no added B-vit was offered ad libitum. Calves were randomly assigned among 3 treatments: rumen protected B-vit blend (RPBV, n = 20); a 30:70 mix of non-protected B-vit blend and fat (UPBV, n = 22); and fat only (CTRL, n = 19). Treatments were fed daily at levels corresponding to 0.39 ± 0.001% and 0.28 ± 0.001% (mean ± SEM) of the SG intake, for the B-vit and fat, respectively. The treatments were weighed into gel caps of varying weights and administered once a day to each calf based on the previous day SG intake. Weaning was from d 49 to d 63. Body growth was measured weekly. Blood was collected at wk 3, 7, 9 and 13, and analyzed for hematocrit (Hem), Plasma Urea Nitrogen (PUN), folates (Fol) and vitamin B₁₂. Data were analyzed as a completely randomized design with a mixed-effects model, using fixed effects of treatment, time, and their interaction, and initial body weight as covariate. Overall ADG (0.99 ± 0.01 kg/d), DMI (1.90 ± 0.02 kg DM/d) and feed efficiency (0.52 ± 0.01) were not different (P ≥ 0.4). In general, plasma B₁₂ levels were not different between RPBV and UPBV (P ≥ 0.5) and a tendency was detected for supplemented vs control at weaning (P = 0.09). No differences were observed for Hem, PUN, or Fol (P ≥ 0.2). Thus, both forms of supplemented B-vit tended to improve vitamin B₁₂ status through weaning. Under the conditions of this study, supplementary vitamins did not improve calf performance.