Adolescents represent 16% of the global population and they are identified as a critical demographic group for promoting sexual health. Adolescents are susceptible to engaging in risky sexual behaviors (RSB) such as early sexual initiation, having multiple sexual partners, substance use during sexual encounters and practicing unsafe sex. Adolescents represent 16% of the global population and they are identified as a critical demographic group for promoting sexual health. Adolescents are susceptible to engaging in risky sexual behaviors (RSB) such as early sexual initiation, having multiple sexual partners, substance use during sexual encounters and practicing unsafe sex. To assess risky Sexual behaviors and associated factors among adolescent in Gedeo Zone, Southern Ethiopia: A community based cross-sectional study. A community based cross-sectional study was conducted in Gedeo Zone among adolescents. A total of 2780 (99.3%) adolescents were participated in the study and gave the response rate of 99.3%. A pre-tested structured questionnaire was used to gather the data and analyzed by using SPSS version 23. During analysis initially bivariable logistic regression model was used then, those variables with a level of significant at a P-value ≤ 0.25 were considered as candidate for multivariable logistic regression model. A level of significant at a P-value ≤ 0.05 was considered as statistically significant in this study. Out of 428 sexually active adolescent 334 (78%) exposed to risky sexual practice. More than half 54.3% of adolescent was protestant in religion followed by Orthodox 34.2% and Muslim 11.5%. In terms of ethnicity, Gedeo 67.4% was the dominant ethnic group in the study area. Mean age at sexual initiation was 15 ± 1.8.Residence AOR 1.14 (1.36-5.25), Sex AOR 2.77 (1.31-5.86), Age AOR 2.01 (1.41-6.39), School attending AOR 1.93 (1.27-5.75), Watching Pornographies AOR 2.51 (1.36-4.62) and Parental monitoring AOR 2.10 (1.07-4.10) were independent predictor of risky sexual practice in this study. The prevalence of risky sexual behavior was found to be alarming among adolescents aged 14-19years, mostly rural and female adolescents and those adolescent start sexual practice earlier exposed to risky sexual practice than their counter parts. Sexual urge, watching pornography and not attending school were the major factor for risky sexual behaviors of adolescent. Parental over all control can protect risky sexual behaviors among adolescent.