Mastitis is an important economic disease-causing production loss in the dairy industry. Antibiotics are becoming ineffective in controlling mastitis due to the emergence of resistant strains requiring the development of novel therapeutic agents. In this study, the authors present the phytochemical synthesis of silver nanoparticles (AgNPs) with acetyl-11- -keto-betaboswellic acid and evaluation of their activity in Staphylococcus aureus induced murine mastitis. Boswellic acid-mediated AgNP (BANS) were oval, polydispersed (99.8 nm) with a minimum inhibitory concentration of 0.033 µg ml-1 against S. aureus, inhibitory concentration (IC50) of 30.04 µg ml-1 on mouse splenocytes and safe at an in vivo acute oral dose of 3.5 mg kg-1 in mice. Mastitis was induced in lactating mice by inoculating S. aureus (log10 5.60 cfu) and treated 6 h post-inoculation with BANS (0.12 mg kg-1, intramammary and ip), and cefepime (1 mg kg-1, ip). BANS treatment significantly (P < 0.05) reduced bacterial load, CRP, SOD, CAT activities and neutrophil infiltration in affected mammary glands. BANS could be a potential therapeutic agent for managing bovine mastitis.