A total of 120 random samples of milk were collected from dairy cows in some examined dairy farms located at different centers of Damietta governorate. California Mastitis Test (CMT), bacteriological and mycological examination were carried out for detection of positive cases of subclinical mastitis. The obtained results revealed that the most bacterial isolates were Staph. aureus, Escherichia coli, coagulase-negative staphylococci, Streptococcus uberis, Corynebcterium bovis and Pseudomonas aeruginosa with prevalence rate of 40%, 30%, 10%, 8.3%, 3.3% and 1.7%, respectively. While, the most frequently mycotic isolate was Candidia albicans with an incidence of 11.7%. Also, the obtained results revealed mixed infection of Staph. aureus and C. albicans in 4 samples and mixed infection of E. coli and C. albicans in 2 samples of cow's milk having subclinical mastitis. None of Staph. aureus strains which isolated from mastitic milk samples produce enterotoxins A, B, C, D or E. In Vitro, antimicrobial suceptiblity test of the bacterial isolates revealed that the most effective antibiotics were Ciprofloxacin, Levofloxacin, Cefataxime and Amoxycillin/Clavulanic acid. While, all bacterial isolates except E. coli were resistant to Cephalexin and Streptomycin. Also, all bacterial isolates except Strept. uberis were resistant to Erythromycin. The most effective antimycotic against Candida albicans was Fluconazole. The obtained results, conclusion, recommendation and preventive measures of subclinical mastitis were discussed