This experiment was conducted to investigate the effect of postpartum calcium supplementation on reducing risk of hypocalcaemia and improving milk production and reproductive performance of dairy cows. In this experiment, the effects of supplementation of 2 calcium boluses at 0.5 and 12 hours postpartum on dry matter intake (DMI), changes in body condition score (BCS), milk yield, blood metabolites and some reproductive functions were investigated. Total of 24 Holstein cows (lactation of 2.8 ± 0.8, and milk yield of 11358 ± 716 kg) were evaluated from 3 weeks before expected date of calving. Cows were grouped according to calcium intake: 1) control group fed formulated diet for fresh cows (CTR), 2) cows fed control diet + 2 calcium boluses. The results showed that DMI (kg/day) was not significantly different (p 0.05) in cows fed calcium bolus (20.43 vs 21.01) compared to control group. The effect of time on DMI was significant (p 0.001), nevertheless the interaction of treatment × time had no effect on DMI (p 0.05). Milk yiled in the first 21 days of lactation in cows receiving calcium boluses was higher (p 0.05) than the control group (39.28 vs. 35.32 kg/day). The effect of time on milk yield was significant (p 0.001), however the interaction of treatment × time had no effect on milk yield (p 0.05). The percentage and yield of milk fat was higher in cows received calcium bolus at 0.5 and 12 hours postpartum (p 0.05). Milk protein percentage and yield, as well as lactose percentage were not affected by calcium boluses (p 0.05), however the changes of protein, lactose and solids non-fat composition (SNF) were affected by time (p 0.001). Percentage and yield of SNF, as well as lactose production in cows receiving calcium boluses were higher than control group (p = 0.05). During the first 8 months of lactation, milk yield was not affected by calcium boluses and interaction of treatment × time (p 0.05). Plasma concentrations of glucose and calcium were not affected by the experimental treatments and interaction of treatment × time (p 0.05). The effect of time showed that, plasma glucose concentration decreased (p 0.001) 72 to 24 hours before calving, then increased (p 0.001) within 24 hours before calving. Before and after calving, the concentration of calcium was not significantly different between the cows fed the control diet or the control diet + calcium boluses (p 0.05). The concentration of calcium increased (p 0.05) from 0.5 to 72 h after calving in both groups of cows. Body fat thickness (BFT) at the beginning of the experiment and the reduction of BFT were not significantly different between experimental groups (p 0.05). However, BFT decreased from d 7 to 21 of experiment in both groups. There were no significant differences for weight of calves at birth, number of insemination, interval to first post-calving insemination, and days open (DO) between experimental groups (p 0.05). Based on the results of this study, supplementation of calcium boluses at 0.5 and 12 hours after calving had a positive effect on increasing milk yield, decreasing days open and decreasing loss of BFT and weight during the first 21 days of lactation. Keywords: Fresh dairy cows, Calcium deficiency, Calcium bolus, Milk yield, Blood metabolites.