Background: Teenage pregnancy is one of the determinants of high maternal morbidity and mortality. Assam is known for its highest contribution of maternal death in India. In Assam, around 31% of teenage girls get married before the age of 18, and around 12% teenage girls become mothers before they turn out to be 18 years. Objectives: The objective of this study is to know the maternal and fetal outcomes of teenage pregnancy and its determinants in a tertiary care setting in Assam. Materials and Methods: A cross-sectional study was conducted among 118 teenage mothers admitted to Jorhat Medical College and Hospital from June to August 2019. Required data on sociodemographic characteristics of the mother, antenatal, intranatal, and postnatal histories, and maternal and fetal outcomes of the pregnancy, were collected in predesigned and pretested schedule. Data analysis was done using Microsoft Excel software. Ethical approval was obtained from the Institutional Ethics Committee. Results: Among the 118 teenage mothers which constitute 14.6% of total deliveries conducted during the study period, 61% were anemic during pregnancy and 75.42% of teenagers had term delivery while 19.49% had either preterm or postterm deliveries. Cesarean section was done for 50.85% of pregnancies and 45.77% of teenage mothers had complications such as eclampsia, prolonged labor, cephalopelvic disproportion, and premature rupture of membrane during labor. About 42.73% of the newborns were found to be low birth weight babies. A statistically significant association was found between determinants such as lower socioeconomic class, younger age at marriage, less education of mothers, lack of knowledge about contraceptives, and teenage pregnancy. Conclusion: Our study findings indicated a high percentage of teenage pregnancy and increased complications among teenage mothers and newborns.