Twenty-five apparent healthy multiparous Holstein cows were examined for subclinical mastitis (SCM). The objectives of the study were to investigate the consequences of SCM on milk composition & blood biochemistry, oxidative stress biomarkers, and the correlation between different milk and serum parameters in SCM-affected cows. The cows were grouped as 16 subclinical infected and 9 healthy according to MSCC and California Mastitis Test (CMT) scores. The blood and milk samples were gathered from each animal and evaluated for compositional, biochemical, and oxidative stress markers alterations. SCM-affected milk samples showed a significant decrease in fat %, protein %, lactose %, TS %, SNF %, and total antioxidant capacity (TAC) and a significant increase in ash %, catalase, and malondialdehyde (MDA) compared with SCM-free milk samples. Milk somatic cell count showed a positive correlation with MDA and catalase. Catalase correlated positively with MDA and TAC. Milk fat showed a positive correlation with lactose, total protein, and albumin and a negative correlation with MSCC, MDA, TAC, and catalase. Significant increase in catalase and total protein associated with a significant decrease in Ca level was recorded in SCM blood samples compared with healthy counterparts. The total protein showed a positive relation with somatic cell count and albumin. Albumin correlated positively with TAC & catalase and negatively with Mg. The results indicate that a significant correlation between different parameters in blood and milk can be useful as a proper clinical indicator for the early detection of SCM in cows.