The aim of this work was to evaluate the antimicrobial activity of Casearia sylvestris (guacatonga), Schinus therebentifolius (Aroeira) and Tabebuia avellanedae (Ipe Roxo) extracts. Three extraction solvents were used (water, ether and alcohol 70%) with three different concentrations: 10%, 20% and 30% plants weight/volume. The inhibitory effect of these extracts on the growth of pathogenic bacteria in domestic animals was evaluated. Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27253, the disk diffusion method in paper Muller Hinton was used. The filter paper discs was soaked with 10 microliters of herbal solution. After 24 hours the growth halos were measured. The inhibition halos larger than 10mm were considered. Controls were made with each solvent extraction. Inhibitory effect was obtained on Staphylococcus aureus with the following extractions: Tabebuia hydroalcoholic 10%, 20% and 30%, Tabebuia ether 10%, 20% and 30%, Tabebuia decoction 20% and 30%, 30% Schinus ether, Schinus water-alcohol 20% and 30% ether and Casearia 10%, 20% and 30 %. The effect was not observed for Escherichia coli and Pseudomonas aeruginosa inhibitory. The extracts obtained from Tabebuia avellanedae had satisfied inhibitory on the Staphylococcus aureus in vitro, followed by those obtained from Schinus therebentifolius and Casearia sylvestris.