Girls aged 10-19 currently represent 12% of Niger's population (2020). And this number continues to grow as the fertility rate is higher while mortality is declining faster. Using Niger's demographic and health surveys carried out between 1992 and 2012, the study investigated adolescent fertility, its trends and associated factors. It mobilised descriptive methods (Total cohort fertility in adolescence (TCFA) computation, distribution of the number of adolescent births, and computation of adolescent cohort childbearing mean age) and multivariate Logistic and Poisson models. The result shows the TCFA went from 1.29 in 1992 to 1.17 in 2012. Early sexual intercourse and marriage, infant mortality, the desire for a large family, and urbanisation are among the factors significantly associated with adolescent fertility in Niger. The study concludes that the high level of adolescent fertility in Niger does not seem to be changing.