BackgroundTeenage pregnancy may adversely affect their health, economic, and social life. Evidence shows that no studies in Ethiopia used decomposition analysis to identify factors for the trend change in teen pregnancy. Therefore, this study aimed to examine the trends and identify contributing factors to teen pregnancy in Ethiopia using multivariate decomposition analysis.MethodWe obtained the data on adolescent women from three Ethiopian Demographic and Health Surveys. A weighted sample of 3266 in 2005, 4009 in 2011, and 3381 teenagers in 2016 were involved in this study. Statistical analysis was performed using STATA 14. Multivariate decomposition analysis was used to identify contributing factors to the change in teen pregnancy. The coefficient value with a 95% confidence interval was used to identify significant factors associated with teen pregnancy.ResultsThe prevalence of teen pregnancy in Ethiopia decreased significantly from 15.9% [95% CI: 14.3, 17.7] in 2005 to 12.5% [95% CI: 10.8, 14.3] in 2016. Multivariate decomposition analysis showed that approximately 83% of the overall change in teen pregnancy over time was due to differences in women’s composition. Age, marital status, education status, working status, contraceptive use, and sexual status before age 18 were statistically significant contributing factors to the decline in teen pregnancy over time.ConclusionThe prevalence of teen pregnancy in Ethiopia decreased significantly over time. The overall decline in teenage pregnancy is due to differences in population composition. Public health interventions should focus on changing cultural norms or attitudes regarding early marriage and pregnancy within religious leaders and uneducated communities.