The antimicrobial activities of the oleoresin (OR) and the essential oil (EO) of Copaifera spp. were checked against microorganisms isolated from milk samples of cows diagnosed with grade III subclinical mastitis. The OR had good antimicrobial activity (MIC ≤ 100 µg/mL) against samples of coagulase-positive Staphylococcus, coagulase-negative Staphylococcus, Streptococcus of groups C, F, and G, and Corynebacterium spp. Meanwhile, the EO had good antimicrobial activity (MIC≤100 µg/mL) against coagulase-negative Staphylococcus and Corynebacterium spp. The OR and the EO were inactive and weak to inactive, respectively, against Escherichia coli. Overall, the OR had better antimicrobial activity than the essential oil against the 55 bacterial isolates (p<0.0001). The GC/MS analysis identified sesquiterpenes in EO and by the ESI FT-ICR MS method, the identification of diterpenic acids in OR was possible. Therefore, this raw plant material is promising for the development of phytotherapeutic drugs against bovine mastitis. Keywords: bovine mastites; ESI FT-ICR MS; essential oil; minimum inhibitory concentration; oleoresin.