Milk provides all of the nutrients that bacteria need to survive and grow. This study was carried out to evaluate physical, chemical and microbial quality in raw cow's milk samples obtained from different dairy markets in Assiut. A total of 25 cow raw milk samples were collected from Assiut city markets. The diversity of Staphylococcus aureus was assessed using Mannitol Salt Agar medium (MSA). Chemical analysis of the milk samples tested indicated that, mineral content was ranged from 0.72 - 3.96 % for total soluble salt (TSS%), 367 to 598 mg/L for Na+, 1.06 - 4.84 mg/L for K+, 24.4 - 311.1 mg/L for Mg2, protein concentrations of the samples varied between 1.7 to 5.63 mg/L. While lipid and lactose concentrations were recorded to be fluctuated between 0.21 - 0.83 mg/L and 0.16 - 0.53 mg/L, respectively. The reported pH of milk samples was weak acidic to neutral (4.54 to 7), Also, the results of the current study showed that the total counts of S. aureus in cow milk were 2x102 – 78x104 CFU/ml and occurred in 92% of the total tested samples. S. aureus was identified morphologically and biochemically. It is characterized morphologically as Gram-positive, non-spore forming cocci, in clusters and showed yellow zone formation around the colonies on MSA medium. Biochemical features of this strain were catalase and coagulase(clotting) positive.