Introduction In spite of the fact that female sex workers being regarded as core transmitters of sexually transmitted infections to the general population, previous studies undertaken around STIs in Ethiopia fail to consider this segment of the population. Hence, the present study investigated the prevalence of self-reported symptoms of STIs and the risk factors among FSWs in Adama Town, Ethiopia. Method A cross-sectional study was conducted from May 01, 2017, to April 30, 2017, in Adama Town. Three hundred ninety female sex workers were selected from 120 licensed drinking establishments by using simple random sampling technique. The interviewer-administered structured tool was used to collect data. Data were entered using EPI data version 3.1 and exported to SPSS version 20 for analysis. Bivariate and multivariable logistic regression analyses were used to identify factors associated with the outcome variable. Result Among the requested 423 female sex workers, 390 willingly responded to the interviewer-administered structured questionnaires making a response rate of 92.2%. One hundred thirty-nine (35.6%, 95% CI (33.8%–37.4%) of the female sex workers reported one or more STI symptoms. Several risk factors were identified including inconsistent condom use with a nonpaying client (AOR = 5.43, 95% CI: 2.73, 10.80), alcohol use before sex (AOR = 2.41, 95% CI: 1.35, 4.30), longer duration of sex work (AOR = 2.27, 95% CI: 1.26, 4.08), and having poor knowledge of STIs (AOR = 2.44, 95% CI: 1.31, 4.54). Conclusion Self-reported symptom of STI among female sex workers in Adama Town is relatively high when compared with previous studies. Hence, health education programs should address the issue of inconsistent condom use with nonpaying clients, alcohol consumption before sex, and knowledge of STIs, with a particular emphasis on those female sex workers who stayed longer in the business.