Introduction: Breast abscess is common infection reported in lactating mother but also occurs in non lactating women. It causes underlying disability and increases morbidity and recurrence which is a major concern in these cases. For treatment, knowledge of microbiological spectrum and proper use of antibiogram is necessary. Material and Methods: The study was performed in SKMCH Muzaffarpur, Bihar from Jan 2018 to December 2019. Pus samples from breast abscess collected and processed for isolation, identification of causative bacterial agent as well as antimicrobial sensitivity test as per standard microbiological protocol. Result: Out of 90 breast abscess patients, 54 bacteria isolated from the samples.The most commonly microorganism was Methicillin resistant staphylococcus aureus followed by Methicillin sensitive staphylococcus aureus ,Proteus spp. and Pesudomas aeruginosa. Conclusion: Methicillin resistant staphylococcus aureus is most commonly pathogenic microorganism causing breast abscess in women in lactational period