A study was conducted to evaluate the effects of thermal indices and relationship with milk yield in dairy cows using invasive (glucose, total cholesterol, triiodothyronine (T3), thyroxine (T4), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and inorganic phosphate) and non-invasive (Rectal temperature (RT), respiration rate (RR), ear temperature (ET) and skin temperature (ST) markers in the Sahel Savannah of Nigeria. Fifteen (15) clinically healthy dairy cows of three breeds; five each from Holstein Friesian purebred, Simmental and Brown Swiss, aged 5-8 years from Sebore Farms were used for the experiment. The animals were maintained on similar feeding programme under hot-dry and cold-dry season. Data collected includes thermoregulatory variables: Rectal temperature, respiration rate, ear temperature and skin temperature), blood biochemical variables (glucose, inorganic phosphate, total cholesterol, triiodothyronine (T3), thyroxine (T4), aspartate aminotransferase (AST), and alanine aminotransferase (ALT), daily milk yield and milk component traits (protein and fat percentage). All the thermoregulatory parameter values differed significantly (P<0.05) between the seasons with the exception of ear temperaturewhich was statistically similar (P>0.05). Rectal temperature, respiratory rate and skin temperature were significantly (P<0.05) higher during hot-dry season compare to cold-dry season.Glucose, ALT and AST differed significantly (P<0.05) across the breeds of dairy cows while cholesterol, phosphorus, T3 and T4 were statistically similar (P>0.05). The serum ALT was higher in Simmental (47.74�1.33iu/l) and Brown Swiss (46.59�1.33iu/l) which differed significantly (P<0.05) from Holstein Friesian cows (39.1�1.33iu/l).However, all the biochemical parameters differed significantly (P<0.05) between the cold-dry and hot-dry seasons with the exception of T3 which was statistically similar (P>0.05).Milk yield was significantly (P<0.05) higher during the cold-dry season (8.03�0.24kg) than the hot-dry season (6.93�0.21kg) while fat (P<0.05) was significantly higher during the hot than the cold season. Holstein Friesian had the highest average daily milk value (8.16kg) while Simmental cow had the lowest milk volume (7.08kg). Simmental and Brown Swiss cows had the highest percentage of fat (4.07%) which were statistically different (P<0.05) from Holstein Friesian (3.88%). Protein showed no (P>0.05) significant difference between breeds. Daily milk yield was significant, low and negatively correlated with temperature (R=-19, P=0.0005) while moderate, significant and negative correlations was observed with THIand RH (R=-0.24, P=0.0005 and R=0.26, P=0.0061) Fat had significant, low and positive relationship with temperature (R=0.17, P=0.0019) while low and positive relationship existed with THIand RH(R=0.19, P=0.76 and R=0.12, P=0.059)than the hot-dry season (6.93�0.21kg) while fat (P<0.05) was significantly higher during the hot than the cold season. Holstein Friesian had the highest average daily milk value (8.16kg) while Simmental cow had the lowest milk volume (7.08kg). Simmental and Brown Swiss cows had the highest percentage of fat (4.07%) which were statistically different (P<0.05) from Holstein Friesian (3.88%). Protein showed no (P>0.05) significant difference between breeds. Daily milk yield was significant, low and negatively correlated with temperature (R=-19, P=0.0005) while moderate, significant and negative correlations was observed with THIand RH (R=-0.24, P=0.0005 and R=0.26, P=0.0061) Fat had significant, low and positive relationship with temperature (R=0.17, P=0.0019) while low and positive relationship existed with THIand RH(R=0.19, P=0.76 and R=0.12, P=0.059). Protein had low and negative correlations with all the environmental factors with the exception of temperature which was positively associated (R=0.003, P=0.9501).Daily milk yield was significant and highly correlated with phosphorus (R=0.52; p=0.02) and T4 (R=0.94; p=0.05) but significant, high and negatively correlated with T3 (R=-0.51).Cholesterol was significant, high and negatively correlated with DMY (R=-0.28). AST was significant, moderately and negatively correlated with DMY (R=-0.26). ALT was negatively correlated with DMY. The regression analysis for prediction of milk yield showed that all the invasive markers combined together best explained daily milk yield (R2= 0.52) in Brown Swiss dairy cows compare to Simmental and Holstein Friesian which were weakly predicted (R2= 0.18). The regression analysis for prediction equation using non-invasive markers, showed that all the non-invasive markers combined together explains only (R2= 0.05) of milk yield when the breeds were pooled. It was concluded that invasive parameters could be a veritable tool in predicting daily milk yield of different genotypes of dairy cows under the Sahel Savannah condition of Nigeria.