Introduction: Early sexual debut has become an emerging global concern, and adolescentsrnwho begin early sexual activity are less likely to use condoms and more likely to havernmultiple partners and early child bearing which intern brings about higher rates of maternalrnand child morbidity and mortality. Higher rates of unintended pregnancy, HIV/AIDS andrnother sexually transmitted infections among adolescents make it fundamental to understandrnfactors associated with early sexual initiation in a wider perspective for designing andrnimplementing effective interventions.rnObjective: To assess the prevalence of early sexual initiation and its associated factorsrnamong in-school adolescents of Addis Ababa.rnMethodology: A quantitative comparative cross sectional facility based study supplementedrnwith qualitative enquiry was conducted from March - April/ 2017 to draw a total sample ofrn548adolescents attendingprimary and secondary education in Addis Ababa. A multistagernsampling technique was applied to select the study participants. A pretested structuredrnquestionnaire was used to collect quantitative data while FGD were used to generaternqualitative information. After data have been collected, Epi data 3.1 was used for data entryrnand cleaned and coded data was analyzed by using SPSS version 20. Bivariate andrnmultivariate analyses were done. Odds ratio with 95% confidence interval was estimated tornidentify predictors of early sexual debut using multivariable logistic regression analysis.rnResult: Ninety two (17.4%) surveyed adolescents have ever had sexual debut and thernprevalence of early sexual initiation in our study was 16.4%.The median age at first sex inrnour finding was similarly 15 years for both community international and governmentalrnstudents.Being encountered pressure from friends to have sex Adjusted OR=7.1(1.7, 28.8),rnusing computer for games and internet for more than two hours/week Adjusted OR=3.5(1.1,rn11.6), not religious Adjusted OR=5.7(1.2, 28.2), RH club member ship, Adjusted OR=11(2.0,rn69.1) perceptions towards father response concerning menstruation will be not helpfulrnAdjusted OR=4.5(1.4, 14.4) were significantly associated with early sexual initiation. Morernover the odds of ever view/see/read pornographic materials was twenty three times higherrnthan who hadnâ€™t viewed Adjusted OR=23.1(1.1, 85.4)rnConclusions and recommendations:-This study indicates that a considerable proportion ofrnadolescents were engaged in sexual activity at an early age and continues to practice riskyrnsexual behaviors and the median age of sexual initiation between governmental andrncommunity intern. In order to delay sexual debut, well designed sexual education whichrnaddress adolescents SRH should be considered