The prevalence of contagious and environmental mastitogenic pathogens was investigated in dairy cattle farms which was categorized as poor, intermediate and high biosecurity levels. Those biosecurity levels were determined according to certain managemental practical procedures noticed in these farms. A total of 190 quarter milk samples were collected from 28 cows and 20 buffaloes from 6 farms in three governments in Egypt (El-Fayoum, Gharbia and Giza). Also, a total of 96 teat swabs were collected during this study, besides 40 swabs from milking cups (milking machine), 24 swabs from floor, 24 from wall and 18 from workers' hands. All milk and environmental samples were tested for total viable colony count and for presence of Enterobacteriaceae, Staphylococcus spp. and Streptococcus spp. Results showed that the mean of total colony count (TCC) was the lowest level in milk samples in intermediate than high and poor biosecurity farms. All environmental samples showed the lowest mean of TCC in high biosecurity farms, while poor and intermediate were nearly the same. Coagulase–positive staphylococcus was isolated from different samples collected from the dairy farms. Teat samples in high biosecurity farms showed the highest risk for coagulase–negative staphylococcus followed by milking cups in poor biosecurity farms. Teat, wall and floor samples in high biosecurity farms were highly contaminated with E. coli. Citrobacter, Klebsiella and Proteus were isolated from different samples. milking cups showed the highest load for Enterococcus in high biosecurity farms. Milking cup in high biosecurity farms presented the highest risk for Streptococcus dysgalactiae, while in intermediate biosecurity farms it was highest in milk samples. Odds ratio is indicated for risk assessment, while Cramer's v and partial omega square are indicated for practical importance. It was concluded that biosecurity programs should be adopted by dairy producers to prevent the chance of mastitis. The biosecurity program needs continuous evaluation at all levels to discover any fault in its application.