IntroductionYouths are defined as individuals within the age group 15–24 years. It is the transitional stage from childhood to adulthood with biological, social, and psychological change, so it is a time of risk and opportunity for their future life. Early sexual initiation exposes young people to various social, economic, sexual, and reproductive health issues, such as unwanted adolescent pregnancies, sexually transmitted infections, unsafe abortion, cervical cancer, and early marriages. Therefore, this study aimed to assess the presence of socioeconomic inequality in early sexual initiation and contributing factors in sub-Saharan African countries.MethodsA total of 118,932 weighted female youths from SSA countries’ DHS data were included in the study. Socioeconomic inequality of Early sexual initiation was evaluated using the Erreygers znormalized concentration index and associated concentration curve. Decomposition analysis was performed to determine those factors causing socioeconomic-related inequality.ResultsThe weighted Erreygers normalized concentration index of wealth-related inequality of early sexual initiation was − 0.157 with a Standard error = 0.0046 (Pvalue < 0.0001); this indicated that early sexual initiation was disproportionately concentrated among the poor (pro-poor). Moreover, the weighted Erreygers normalized concentration index (ECI) of educational status-related inequality of early sexual initiation was − 0.205 with a Standard error = 0.0043 (Pvalue < 0.0001). This indicated that early sexual initiation was disproportionately concentrated among youths with no formal education. The decomposition analysis revealed that mass media exposure, wealth index, place of residency, religion, marital status, educational status, and age were significant contributors to the pro-poor socioeconomic inequalities in early sexual initiation.Conclusion and recommendationThis study has revealed pro-poor inequality in early sexual initiation. Therefore, priority must be given to modifiable factors such as promoting the accessibility of media exposure in the household, improving the educational opportunity of female youths, and improving their country’s economy to a higher economic level to improve the wealth status of the population.