This study uses annual time series data of adolescent fertility rate for Tanzania from 1960 to 2020 to predict future trends of adolescent fertility rate over the period 2021 to 2030. The study utilizes Holt’s linear exponential smoothing model. The optimal values of smoothing constants α and β are 0.9 and 0.3 respectively based on minimum MSE. The results of the study indicate that annual adolescent fertility will continue to decline but still remain very high throughout the out of sample period. Therefore, we encourage authorities in Tanzania to scale up awareness campaigns among the communities, support girl child education, fund empowerment programs for youths and strictly enforce laws that protect sexual and reproductive health rights of girls and women in order curb child marriages.