Background For decades, Ethiopians have employed ethnoveterinary medicinal plants to cure both human and livestock ailments. Currently, few studies have been conducted on antimicrobial activity evaluation in Ethiopia. This study, therefore, is designed to evaluate the antibacterial activities of selected ethnoveterinary medicinal plants used in treating livestock ailments in the study area. Methods Ethanol extracts of plants obtained by maceration of roots and leaves of four medicinal plant species were studied for potential antimicrobial activity using a disc diffusion method against S. aureus and E. coli . Data obtained from experiments were analyzed using ANOVA and the significant test was set to P < 0.05. Results The antibacterial properties of four ethanol extracts of leaves of Withania somnifera L., Becium obovatum, Ageratum conyzoides L., and root of Pentas lanceolata (Forssk.) Defiers were evaluated in vitro and found to be effective against S. aureus but not E. coli . There was no significant difference between the studied plant species and concentrations (p > 0.05), according to the results. The four test extracts had minimum inhibitory concentrations (MICs) ranging from 6.25 to 25 mg/mL, with inhibitory potential ranging from 12.5 to 100 mg/mL. Pentas lanceolata (Forssk.) Defiers’s antibacterial activity at a concentration of 100 mg/mL (18.67 3.78 mm) was comparable to the standard antibiotic (Gentamicin 20g per disc), which had a measurement of 23.08 ±0.9 mm. Conclusion This finding on the selected medicinal plants of Dawuro Zone supports the traditional claims of effective antimicrobial activity in the treatment of livestock health management. Hence, the study suggests further investigations need to be conducted to isolate and elucidate active ingredients in the plant materials tested.