Background: Sexually transmitted infection (STI) is a major global cause of acute illness, infertility, long-term disability and death, with serious medical and psychological consequences to millions of men, women and infants. Moreover, in Ethiopia, epidemiological studies on STI among STI clinic clients are limited. Therefore, the aim of this study was to determine the prevalence and associated risk factors of sexually transmitted infection (STI).Methods: A cross sectional study was conducted between April and August 2014 among STI clinic clients in Gondar Town hospitals and health centers. One hundred twenty study participants who fulfill the criteria were included. Different laboratory methods and techniques were applied to identify the possible microorganisms. Data were entered and analyzed using SPSS version 20. Logistic regression was used to determine risk factors for STI and P values < 0.05 was considered statistically significant.Results: The overall laboratory test confirmed that STIs prevalence was 74.1% with 32.5% being Candida spp., 30% T. palladium, 20.8% N. gonorrhoeae and 14.2% T. vaginalis. Two or more organisms were isolated in 20% of the study subjects. Risk factors for STI had knowledge about STI and alcohol consumption.Conclusion: The prevalence of N. gonorrhoeae, T. pallidum, T. vaginalis, and Candida spp. in the study area was high. It needs health education programs, promotes condom utilization and more comprehensive community based STI studies.Keywrds: STI, Candida spp., N. gonorrhoeae, T. pallidum, T. vaginalis