This study was carried out to evaluate the effect of macroalgae (Halimeda opuntia) and yeast culture (saccharomyces cerevisiae) as feed additives on body performance, some blood plasma constituents, some rumen parameters and nutrients digestibility of growing lambs. Fifteen Ossimi lambs 5-6 months old and 25.51 ± 2 kg live body weight were randomly divided into three equal groups (5 animals each). Control group (CON) was fed the basal diet and other two treatment groups were fed the same basal diet, supplemented with either 1% macroalgae powder (ALG) or 1% yeast culture (YC). Lambs were weighed to determine performance of growing lambs and adjusted the requirement. Blood samples were collected monthly from all animals before morning feeding. Rumen samples were collected to determine ruminal pH values, ammonia-N concentration and total volatile fatty acids (TVFAs) concentration. The digestibility trials were carried out to evaluate nutrients digestibility of the different experimental rations. Final body weight and total gain not affected by treatments. Lambs of ALG group had the worst feed conversion ratio compared with YC and CON group. Ruminal pH, ammonia-N concentration and TVFAs were not affected by treatments. Dietary yeast or macroalgae increased (P<0.05) blood plasma total protein and albumin concentrations, while decreased (P <0.05) plasma urea -N concentration compared with those of control animals. Dietary macroalgae increased (P<0.05) DM, OM, CP, CF and NFE digestibility compared with YC and CON groups. In conclusion, macroalgae and yeast culture as feed additives may have a beneficial effect on nutrients digestibility and blood metabolites of Ossimi sheep male.