Abstract Background The prevalence of pregnancy-induced hypertension in Ethiopia ranges from 2.2 to 18.3%. 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. Pregnant mothers diagnosed with PIH during the data collection period in the selected hospitals were included as exposed group and normotensive women were also enrolled as a control group. This study addresses women diagnosed with preeclampsia, eclampsia and gestational hypertension between 28 and 35 weeks of gestation. Data were collected using an interviewer-administered questionnaire and review of their medical records from February 2018, to February 2019. The adverse perinatal outcome event includes low birth weight, birth asphyxia, small for gestational age, preterm delivery, admission to neonatal intensive care unit and perinatal death. 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 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.