This systematic review and meta-analysis compared the effect of multiple-micronutrient (MMN) supplementation vs iron and folic acid (IFA) supplementation among adolescents on maternal morbidity, birth outcomes, and mortality outcomes. Additionally, the meta-analysis compared the effects of MMN supplementation on adolescents compared with the effects on adult women, and assessed potential effect modification of MMN supplementation by baseline and geographic characteristics of adolescents. Results of the meta-analysis suggest that multiple-micronutrient supplementation can improve birth outcomes among pregnant adolescents in low- and middle-income countries more than IFA supplementation, and support the need for policy change.