This study was conducted to examine the effect of feed probiotics substituents in serum biochemistry and carcass characteristics of tropically bred exotic turkey. A total of 80 British united turkey (BUT) were assigned to 4 dietary treatments consisting of 4 supplemental levels of equal mixtures of RoxazymeG2 ® at 200 ppm, 250 ppm, 300 ppm and 350 ppm. The polynomial contrast (linear and quadratic) was applied to determine the effect of inclusion of varying mixtures of enzyme and yeast supplementations using SPSS 1999. At starter phase (5-8 weeks), turkeys fed diet containing combination of 200 ppm enzyme and yeast recorded highest (P < 0.05) PCV, Hb, WBC, RBC and glucose values. AST and serum uric acid values were highest (P<0.05) for turkeys fed diet containing combination of 350 ppm enzyme and yeast. At grower phase (9-12 weeks), the values of WBC reduced significantly (P < 0.05) with increased combination of enzyme and yeast levels in the diet whereas RBC recorded higher values. Turkeys fed diet containing combination of 200 ppm enzyme and yeast recorded a significantly (P < 0.05) high values of total serum protein and serum globulin relative to other combination levels. At finisher phase (13-16 weeks), birds on 350 ppm combined supplementation of enzyme and yeast recorded a significantly (P < 0.05) higher PCV HB, ALT and WBC compared to other treatments. The value for uric acid was significantly (P < 0.05) elevated in birds fed 200 ppm and 300 ppm enzyme and yeast combination. There was no significant (P > 0.05) effect of enzyme and yeast supplementation on live weight, dressing percentage, weights of head, neck, drum stick, thigh, breast, lungs, liver, heart, kidney, spleen, gizzard, proventriculus, crop and abdominal fat except back weight and wing weight that were significantly (P<0.05) affected by dietary treatment. In conclusion, inclusion of feed additives in MSP diet such as enzymes and yeast is a good measure in enhancing serum biochemistry and production performance of exotic turkey bred in the humid tropics.