The mammary gland of primiparous dairy heifers is highly susceptible to intramamary infections. Both pre - calving and post-calving secretions had clinical and subclinical mastitis. They were found infected by different bacteria and the dominant bacteria species isolated were S. aureus, C. bovis and coagulase negative staphylococcus (CNS). The mean Somatic cell count was also found to be high. The overall prevalence of both clinical and sub clinical mastitis was estimated to be 48.6% at quarters level. The majority of isolates were sensitive to in-vitro antibiotic sensitivity test. However, many of S. aureus species wereresistant to streptomycin, penicillin,lincomycin and oxyteracyline. Intramammary infection of primiparous dairy heifers both at pre-calving (at third trimester of pregnancy) period and early lactation with different pathogens was evidenced in this study. From this it was concluded that the hypotheses that always argue primiparous dairy heifers are free from intramammary infection by many farmers and others will no longer be valuable and advocated.