This study was designed to evaluate the effect of Saccharomyces cerevisiae ¹⁰²⁶ and Lactobacillus casei on some ruminal and biochemical parameters in sixty healthy fattening calves in a private dairy farm at Sharkia Governorate, Egypt. Three groups were included in the experiment, each contains 20 calves. The first Group (G1) served as a control that received a basal diet as total mixed ration. The second (G2) and the third (G3) Groups received the same ration in addition to Saccharomyces cerevisiae ¹⁰²⁶ and Lactobacillus casei, respectively, both were added by 5 g per head per day for three months experiment. Blood samples were collected monthly for three times. The results demonstrated that supplementation of Saccharomyces cerevisiae ¹⁰²⁶ and Lactobacillus casei to calves' feed improved fecal, respiratory and locomotors scores. They increased the ruminal contraction (3.66 ±0.33/2 minutes), protozoal population and activity and total volatile fatty acids (87.66 ±1.45 mmol/L). On the other hand, both supplements reduced the ruminal ammonia concentration (25.16 ±1.12 mmol/L), but ruminal juice pH was elevated in case of Saccharomyces cerevisiae ¹⁰²⁶ (6.53 ±0.06) and stabilized in case of Lactobacillus casei supplementation. Saccharomyces cerevisiae ¹⁰²⁶ and Lactobacillus casei significantly increased serum levels of β-hydroxy butyric acid (0.29 ± 0.02 mmol/L) while decreased level of non-esterified fatty acids (1.80 ±0.15 mmol/L and 1.81 ±0.14 mmol/L, respectively). Aspartate transferase showed significant reduction in Saccharomyces cerevisiae ¹⁰²⁶(57.0 ±21.4 U/L)and Lactobacillus casei (68.66 ±9.49 U/L) supplemented groups, while alanine transferase and gamma-glutamyl transferase showed only reduction (10.33 ±13.83 U/L and 9.06 ±0.88 U/L, respectively) in Lactobacillus casi supplemented group. There was a significant increase in reduced glutathione GSHand glutathione peroxidase GPX in G2 and G3, while Malone dialdehyde MDA of G2 and G3 showed insignificant reduction in comparison with G1. Weight gain was significantly improved in Saccharomyces cerevisiae ¹⁰²⁶ supplemented group compared with Lactobacillus casei and control ones. The results suggested that supplementation of Saccharomyces cerevisiae ¹⁰²⁶ and Lactobacillus casei to fattening calves feed has a positive impact on calves' general health and their weight gain.