Background: Globally adolescents are facing a range of sexual and reproductive health problemsrnlike unwanted pregnancy, unsafe abortion, STI including HIV. In addition, uptake ofrnreproductive health services among adolescents remains low. Several factors are implicated forrnpoor uptake of contraceptive methods among adolescent girls. However, adolescents’ motherrnknowledge and attitude towards contraceptive methods on adolescent contraceptive utilizationrnhas not been adequately studied. rnObjective: To assess the prevalence of contraceptive use and associated factors amongrnunmarried female adolescents. rnMETHODS: A community based cross-sectional design with both quantitative and qualitativernmethods was conducted in Butajira South Central Ethiopia with a sample size of 491 unmarriedrnfemale adolescent and their mothers. A multi stage sampling technique was used. Interviewerrnadministered pre-tested structured questionnaire and interviewer topic guide was used to collectrndata for quantitative and qualitative respectively. The data was entered into Epidata and exportedrnto STATA for analysis. The quantitative data analysis includes descriptive, bivariate and rnmultivariate logistic regression analysis. Content analysis was use to analyze the qualitative data.rnResult: A total of 491 unmarried female adolescent & their mothers were approached of which rn450 gave consent to participate in the study giving a response rate of 90.4%. The prevalence ofrncontraceptive use among sexually active adolescent was 43(15.2%). A unit increase inrnadolescents’ mothers knowledge score on contraceptive methods is associated with an increase inrnthe odds of ever use of contraceptives among adolescent by 1.32 [AOR=1.32: (95%CI: 1.121.46)].rnrnFurthermore ever use of contraceptive was found to be significantly associated withrnadolescents age [AOR=3.8 (95% CI: 1.33, 10.8)] and adolescents knowledge on contraceptivern[AOR=1.23 (95%CI: 1.12-1.47)]. Our qualitative findings showed that majority of adolescents’rnmother do not advise use of contraceptives by their adolescent girls. rnConclusion and Recommendation: Prevalence of contraceptive utilization among unmarriedrnsexually active adolescent in BHDSS was low and maternal knowledge of modern contraceptivernwas found to be significantly associated with adolescent’s contraceptive use. Therefore Policyrnmakers and programmers should strengthen different programs to improve contraceptivernutilizationamongadoelscents.