Background: Preeclampsia is defined as the onset of a new episode of high blood pressure in a woman usually after 20 weeks gestation plus proteinuria, whereas eclampsia is defined as generalized seizures in a pregnant woman who generally has preeclampsia criteria. Preeclampsia and eclampsia are hypertensive disorders of pregnancy and thus, among the top causes of maternal death worldwide. The objective of this study was to investigate risk factors for preeclampsia/eclampsia. Methods: This was a hospital-based unmatched case-control study carried out among women of reproductive age (15-49 years) who have given birth at Nairobi County Hospitals and admitted to the postnatal ward July-September 2019 with a sample size of 352 participants (88 cases and 264 controls). All cases were selected, while controls were simple random sampled, as per eligibility criteria. Information or data were gathered using a structured interviewer-administered questionnaire and data abstraction tool. Descriptive analysis was carried out, where, categorical variables were presented in percentages or proportions, whereas; continuous variables were presented in means, standard deviations, and range. This was followed by a bivariable mixed-effect logistic regression analysis and a multivariable mixed-effect logistic regression analysis using the significant variables from bivariable analysis. Results: Of all the 88 cases enrolled in the study 5 (5.68%) had eclampsia and 83 (94.32%) had preeclampsia. There was a significant association between personal history of hypertension (AOR=7.1; 95% CI: 2.6-19.3, p=0.001), Occupation as a housewife (AOR=3.1; 95% CI: 1.1-8.8, p=0.034), nulliparity (AOR=7.5; 95% CI: 1.5-37.5, p=0.015) ,  primiparity (AOR=2.1; 95% CI: 1.1-4.2, p=0.031), advanced maternal age 35-49 years (AOR=5.9; 95% CI: 1.1-33.3, p=0.042), and the occurrence of preeclampsia/eclampsia. Conclusions: The following conclusions were made regarding the study findings: Personal history of hypertension, older/advanced maternal age (35-49 years), occupation, and parity were factors significantly associated with preeclampsia/eclampsia.