Obesity is one of the factors causing preeclampsia. Based on observational survey data at the Afifa Primary Clinic and Maternity Clinic in Prambon conducted during the month of August 2017, out of 10 pregnant women 1 had severe pre-eclampsia, 1 person had mild preeclampsia, and 1 person with gestational hypertension. The data shows the high incidence of preeclampsia in the Afifa Primary Clinic and Maternity Clinic in Prambon. The purpose of this study was to determine the relationship of obesity in pregnant women with the incidence of preeclampsia. The research design used was a retrospective analytic survey with chi-square statistical tests using software to determine the relationship. The study population was pregnant women who made a pregnancy visit in the Sidoarjo General Hospital during January-June 2018 totaling 258 mothers. And the sample taken was 157 mothers and was taken by systematic random sampling. The results showed that preeclampsia was more experienced by obese mothers (37.6%) when compared to non-obese mothers (11.1%). While the condition of not preeclampsia is more experienced by mothers who are not obese (88.9%) when compared with mothers who are obese (62.4%). The Chi square test results obtained p value <0.001 which means p <α so that H0 is rejected. It can be concluded that there is a relationship between obesity and the incidence of preeclampsia in pregnancy. So it is recommended to health workers to improve intensive care for obese mothers to reduce the incidence of preeclampsia.