BACKGROUND: The burden of HIV infection among key population like female sex workers (FSW) is higher and challenges the prevention and control of the virus compared to other population groups. HIV self-testing allows people to test themselves discreetly and conveniently and may provide opportunities to people not currently reached by existing HIV testing and counseling services. Hence, this study aimed to assess the magnitude of HIV Self-Testing (HIVST) and associated factors among Female sex workers in Waliso Town in Central Ethiopia. METHOD: A community-based Cross-sectional study was conducted from 1 October-November 30, 2023, among female sex workers using snowball sampling. A total of 400 participants were included in the study. Data was collected using pre-tested, structured self-administered, and interviewer-administered questionnaires using face-to-face interviews. A binary logistic regression model was fitted using SPSS version 26 to identify factors associated with HIV self-testing. Adjusted Odds Ratio (AOR), 95% confidence interval, and a p-value < 0.05 was used to judge the statistically significant variables. RESULTS: The prevalence of HIV self-testing among female sex workers in Waliso town was found to be 37% (95% CI: 32, 42). Education status (attended high school and above) (AOR = 7.62[95% CI 2.55,24.67], marital status (divorced) (AOR = 2.1[95% CI 1.23,3.6], those whose both parents dead (AOR = 2.72[95% CI 1.4,5.28] and before sex whether they asked their partner test status (AOR = 0.17[95% CI 0.07,0.37] were statistically significant. CONCLUSION: This study revealed that HIV self-tests among female sex workers were lower than the 95% national target. Education status, marital status, parent`s living status and knowing the partner HIV status before sex were found to be predictors of HIV self-test. Our findings underscore the need to develop evidence-based strategies to improve HIV testing uptake by FSWs and improve community-based services.