Objective: This study was aimed to assess the prevalence of pulmonary tuberculosis and its associated factors among adults living with HIV/AIDS attending Public Hospitals, Shashamene Town, Oromia Region, South Ethiopia. Methods: A cross-sectional study was conducted from November 2020 to February 2021 among Adults Living with HIV/AIDS attending Public Hospitals in Shashamene Town, Oromia Region, South Ethiopia. A sputum sample was collected and analyzed using Xpert MTB/RIF assay and blood sample was collected to count CD4 using BD FACSPresto analyzer. Semi-structured questionnaires were used to collect data. SPSS version 25 software was used for statistical analysis and a p value of <0.05 was considered as statistically significant. Results: In this study, the overall prevalence of pulmonary tuberculosis among adults living with HIV/AIDS attending the Public Hospitals was 23.5% (5% confidence interval: 18.26, 29.13). Variables such as age range of 50–64 years, female gender, occupation with house wife, and World Health Organization stage (III and IV) were significantly associated with prevalence of tuberculosis infection. Conclusion: The prevalence of tuberculosis in our study site was high. There is a need for regular screening of people living with HIV/AIDS for TB using highly sensitive method like Xpert MTB/RIF assay to know their TB status as well as early commencement of anti-TB.