Background <p>Preeclampsia and eclampsia are severe complications of pregnancy that significantly contribute to maternal and fetal mortality. A comprehensive understanding of the predictors of these conditions is essential for developing effective interventions. Despite preeclampsia and eclampsia being among the leading contributors to maternal and fetal mortality in resource-limited areas in Kenya, especially the arid and semi-arid regions such as Garissa, limited studies have specifically examined the predictors of maternal and perinatal mortality among women with preeclampsia and eclampsia. Therefore, this study aimed to investigate the predictors of perinatal and maternal mortality among pregnant women with preeclampsia and eclampsia at Garissa County Referral Hospital.</p> Methods <p>A retrospective cohort study was used to evaluate the records of 138 eligible pregnant women diagnosed with preeclampsia and eclampsia from 1st January 2019 to 31st December 2023. The study aimed to determine the predictors of maternal and perinatal mortality among pregnant women diagnosed with preeclampsia and eclampsia. A data abstraction tool capturing sociodemographic, clinical, treatment modalities, and outcome variables was used to collect data. Descriptive analysis was used to present mortality rates and management modalities, while binary logistic regression was used to determine the predictors of mortality among preeclampsia and eclampsia patients.</p> Results <p>The mean age of the participants in this study was 26.86 ± 7.6 years. There were higher cases of preeclampsia (63.0%) than eclampsia (37.0%) observed. Maternal mortality was 13.0%, while the perinatal mortality was 42.7%. The findings indicated that 34.1% of patients had a postpartum haemorrhage and 14.5% had a placental abruption. Neonatal complications were observed in 26.0% of the fetuses, with respiratory distress being the most prevalent (20.0%). Diabetes mellitus (AOR = 8.9, 95% CI = 2.1–41.4, <i>p</i> = 0.003) and multigravida status (AOR 3.6, 95% CI = 1.6–8.5, <i>p</i> = 0.002) were the significant predictors of maternal and perinatal mortality, respectively.</p> Conclusion <p>The maternal and perinatal mortality among mothers with preeclampsia and eclampsia was comparable to the rates reported in similar settings. The significant predictors of maternal and perinatal mortalities were diabetes and multigravida status, respectively, highlighting the need for timely antenatal care and close monitoring for multigravida women and those with pre-existing conditions like diabetes.</p>