The aim of this study was to evaluate the antimicrobial activity and minimum inhibitory concentration (MIC) of copaiba oil, extracts of Passiflora cincinnata and substances commonly used against endodontic infections of bacterial strains certified by the American Type Culture Collection (ATCC) and against clinical isolates (CI). The methodology involved the preparation of crude extracts of the plants, the selection of copaiba oil and the standardization of samples. The antibacterial activity of these substances was tested against Enterococcus faecalis (ATCC), Escherichia coli (CI) and Pseudomonas aeruginosa (ATCC and CI). The MIC was determined by broth dilution and the nitroblue tetrazolium chloride dye reduction test. The data were statistically analyzed by the Kolmogorov-Smirnov normality test and by the Kruskal-Wallis test with a confidence level of 95%. The analysis of the antimicrobial activity showed that the ethanol extracts of P. cincinnata and the combination of calcium hydroxide with polyethylene glycol with and without camphorated monochlorophenol showed no antimicrobial activity. However, the copaiba oil and other substances evaluated showed some antimicrobial activity against the microorganisms used (p <0.01), exhibiting a MIC ranging from <0.3 to >400 µL/mL (p <0.05). Copaiba oil showed antimicrobial activity and could represent a potential phytotherapeutic agent to be used against microorganisms causing endodontic infections.