The objective of this study was to evaluate the effect of Bacillus subtillis (BS) and Bacillus licheniformis (BL) spores supplementation on performance, general health and some serum constituents in Holstein suckling calves. A total number of 36 newborn pure-bred Holstein calves (5 days old, with an average body weight of 44.27±0.37 and 42.87±0.55 Kg for males and females, respectively) were randomly divided in to three homogeneous groups (12 calves per group, 6 of each sex). For 30 consecutive days, all groups were fed whole milk three times daily. Once a day, 0, 10 and 20 g of the tested probiotics powder dissolved in the whole milk to represent G1 (control), G2 and G3, respectively. Each gram of this powder contained 2×109 cfu of BS + 2×109 cfu of BL. Offering the starter mixture to calves began on the 8th day of life. The same parameters were investigated for another 30 days after the end of the probiotics treatment. The obtained results revealed that the overall TDMI value did not affected the first 30 days, but it significantly (P<0.001) increased in posttreatment period in G2 than those in G1 and G3. During the two experiment phases, the ADG of G2 calves was better (P<0.001) than those in the other tested groups. At the end of the trial, the G2 calves were 8.68 Kg heavier than the control calves. Consequently, the weaning age was earlier in G2 than in other tested groups. The incidence of diarrhea and its duration declined in G2 calves compared with G1and G3 calves. The highest percentage of pneumonia incidence was observed with the calves in G1. The concentrations of serum glucose, total protein, creatinine and activities of ALT and AST did not vary (P≥0.05) among all tested groups. On the other hand, albumin level were decreased (P=0.02) in G2 and G3, while globulin level was elevated (P=0.02) in G2 compared with those in G1, but these levels stayed within the normal range. Additionally, the triglycerides and cholesterol mean values were significantly (P=0.001) lower in G2 and G3 than in G1. However, serum immunoglobulin G concentrations were significantly (P=0.001) increased in G2 and G3 after 15 days of the probiotics addition compared to that in G1. The economic evaluation showed better return with the low dose of probiotics (G1) than the other groups. Conclusively, supplementing whole milk with BS plus BL spores had beneficial effects on the performance and health of the suckling Holstein calves.