Background: Pregnancy-induced hypertension is the development of new hypertension with or without proteinuria after 20 weeks of pregnancy. The prevalence of pregnancy-induced hypertension in Ethiopia ranges from 2.2 to 18.3%. Similarly, a study conducted in Tigray regional state indicated a higher prevalence of pregnancy-induced hypertension. However, so far little is known about the adverse perinatal outcomes of pregnancy-induced hypertension in Tigray Regional State, Ethiopia. Therefore the objective of this study was to assess the effect of pregnancy-induced hypertension on adverse perinatal outcomes in Tigray Regional State, Ethiopia. Methods: a prospective cohort study was conducted on a total sample of 782 pregnant women attending antenatal care in hospitals of Tigray regional state, Ethiopia. Data were collected using interviewer-administered questionnaire and review of their medical records from February 1, 2018, to February 30, 2019. Maternal age, wealth status, educational status, residence, gravidity, type of pregnancy, mode of delivery, anemia status and maternal undernutrition variables were controlled in the statistical models. A modified Poisson regression model with robust standard errors was used to analyze Relative risk. Results: In this study, the overall incidence of adverse perinatal outcome was higher among women with pregnancy-induced hypertension than normotensive women (66.4% vs 22.2%). After adjusted for confounders women with pregnancy-induced hypertension were born babies with a higher risk of low birth weight (adjusted RR(95%CI)= 5.1(3.4,7.8)), birth asphyxia (aRR=2.6(1.9,3.8)), small for gestational age (aRR=3.3(2.3,4.6)), preterm delivery (aRR=5.2(3.4,7.9)), stillbirth (aRR=3.46(1.40,8.54)), admission to neonatal intensive care unit (aRR=5.1(3.1,8.4)) and perinatal death (aRR=3.6(1.8,7.4)) compared to normotensive pregnant women. Conclusions: Higher incidences of adverse perinatal outcomes were occurred among women pregnancy-induced hypertension in Tigray regional state, Ethiopia. Hence health care providers should strengthen prevention, early diagnosis and prompt management of pregnancy-induced hypertension to reduce adverse perinatal outcomes of pregnancy-induced hypertension. Keywords: Adverse perinatal outcomes, pregnancy-induced hypertension, Tigray, Ethiopia