Purpose: Canine leptospirosis and brucellosis are significant zoonotic gram-negative bacterial diseases that affect humans and animal species. This study was aimed to estimate the seroprevalence and assess associated risk factors of canine Leptospira and Brucella species infections in Ambo, Bako, and Gojo Towns, West Shewa Zone, Ethiopia. Methods: A total of 385 serum samples were collected from randomly selected dogs. Antibodies against Brucella and Leptospira species infection were tested using the Enzyme-Linked immunosorbent Assay technique (ELISA). A structured questionnaire survey was administered to each dog-owning household to gather information on potential risk factors. The association between independent and outcome variables was analyzed using the Chi-square test followed by univariable, and multivariable logistic regression analyses. Results: The overall seroprevalence of Brucella and Leptospira species infections were found to be 15.06% (95% confidence interval (ci): 11.64– 19.04%) and 4.16% (95% ci: 2.39– 6.67%), respectively. Multivariable logistic regression analysis showed that the town was the significant risk factor of Brucella species infection seropositivity. Accordingly, dogs found in Gojo ((odds ratio (OR)): 17.72 CI: 1.17– 117.54, p=0.036) and Bako (OR: 7.99, 95% CI: 0.96– 66.37), p=0.054 towns were more at risk to be infected with Brucella species than dogs living in Ambo. Conclusion: The seroprevalence of Leptospira and Brucella species infections in dogs of the West Shewa Zone was high and moderate, respectively, suggesting the possible transmission of the disease between dogs and other animals. These infections might be an under-recognized threat to public health and animal welfare. Further research on the identification of the serovars of Leptospira and biotypes of Brucella circulating in dogs is encouraged. Finally, knowledge of the comprehensive epidemiology of these diseases is an invaluable input for veterinarians, healthcare professionals, and policy-makers to avoid or manage canine leptospirosis and brucellosis.