BACKGROUND: Adolescent pregnancy and fertility are often discussed in literature asrncauses of health concern and as a social problem. High teenage fertility is recognized as arnworldwide challenge given its adverse consequences. In sub-Saharan Africa, adolescentrnchildbearing remains common. Maternal and child mortality is greatly affected by adolescentrnpregnancy and contribute hugely to the vicious cycle of ill-health and poverty.rnOBJECTIVES: To examine the determinants of adolescent fertility in Oromia NationalrnRegional State of Ethiopia.rnMETHODS: A cross-sectional sample survey design using stratified cluster samplingrnmethod by the Ethiopian Demographic Health Survey 2016 (EDHS-2016) was used. After therndata for adolescents aged from 15 to 19 years were extracted from the large data set,rndescriptive statistics and logistic regression were done. Multivariable logistic regressionrnmodel was fitted to identify socio demographic and economic determinants of adolescentrnfertility.rnRESULTS: A total of 415 adolescent girls from Oromia regional state were included in thernselected sample in EDHS-2016. The prevalence of adolescent girls who ever had a child orrnpregnant was 17 %. Adolescents who had no education and primary education were 5.5 andrn5.3 times more likely to have a child or be pregnant than those with secondary and aboverneducation respectively. [AOR=5.5; 95%CI (1.38,22.29)] [AOR=5.3; 95% CI (1.53,18.46)]rnThose ever married adolescents were 138 times more likely to have a child or be pregnantrnthan never married adolescents. [AOR=138.7; 95% CI (70.83, 271.83)rnCONCLUSION: A considerable proportion of female adolescents in Oromia regional staternhad a child or was pregnant already. Being married and at low level of education werernsignificant predictors of adolescentsâ€™ fertility status. In addition even though almostrnuniversally adolescents know about contraceptives (97%) utilization level is very low (4%).rnRECOMMENDATION: Concerned stakeholders should work towards supporting girlsâ€™rneducation and delaying marriage of adolescent girls