Transition from pregnancy to lactation in dairy bufallo cows involves considerable metabolic adaptation. Additional stress is incurred during infections such as post-partum mastitis. The effect of naturally acquired bacterial infection of the buffalo udders on the activity of the milk triiodothyronine (T₃) content, from healthy (control) and inflamed quarters, was determined to develop a better understanding of thyroid metabolism in buffalo. The diagnostic procedure included history and clinical examination of the udder, macroscopic evaluation of secretions, the California Mastitis Test (CMT), determination of somatic cell counts, bacteriological examination of milk and some biochemical parameters (AST, ALP, LDH, Malondialdehyde, calcium, phosphorus, sodium and chloride) of the same milk samples. The associations between T₃ and other milk constituents were investigated, as well as the relationships between the bacterial species isolated from milk and others biochemical parameters. Bacterial examination, somatic cell counts (SCC) and the percentages of milk constituents were analyzed in 42 buffalo cows suffering from subclinical mastitis in one or more than one udder quarters, as well as from 8 healthy control buffalo cows. In single bacterial isolation, E.coli was the highest isolated bacteria from different scores of SCC (19 %) followed by coagulase negative staphylococcus (CNS) and other streptococci (14.3 % for each) meanwhile the Staphylococcus aureus (S.aureus) was the lowest isolate (9.5%). On the other hand, in mixed bacterial infection E.coli with S.aureus and other strept. was the highest categegory (16.7 %) followed by S.aureus with E.coli (14.3 %) while CNS with E.coli  was the lowest one (11.9 %) .It has been found that milk parameters from inflamed quarters were decreased when compared with controls. The decrease in the milk T₃ from subclinical mastitic buffaloe cows was manifested when somatic cell counts were > 5 ×10⁵ / ml milk. These results suggest that the marked decreased T₃ level and different milk contents in mammary secretions during naturally occurring subclinical mastitis is associated with the severity of inflammation. Milk enzymes (AST, ALP and LDH) as well as Malondialdehyde, calcium and phosphorus were detected. Significant elevation of liver enzymes, sodium and chloride were noticed in subclinical mastitis cases than healthy control udder. This study confirms the close inter-relationship between the thyroid hormone (T₃), biochemical parameters and different milk constituents and the severity of bacterial infection causes udder mastitis in addition to bufallo udder health.