OBJECTIVE To compare choroidal thickness (CT) measurements in preeclamptic and healthy women in the third trimester of pregnancy using optical coherence tomography. METHODS This cross-sectional study included 148 eyes of 74 women, divided into two groups: 27 healthy pregnant women in the third trimester (control group) and 47 age-matched pregnant women in the third trimester with preeclampsia (PE group). Of the 47 subjects in preeclampsia group, 26 were classified as having mild PE and 21 as having severe PE. Choroidal thickness was measured at ten different locations: at the fovea and every 500 µm from the fovea up to 2500 µm temporally and up to 2000 µm nasally. RESULTS Comparing CT of both groups, choroid always tended to be thicker in subjects with preeclampsia in comparison with healthy pregnant women, with statistical significance in nasal measures. Dividing PE group according to disease severity, women with severe preeclampsia tended to have thicker choroids in comparison with mild preeclamptic and healthy pregnant women. Choroid was also significantly thicker in preeclamptic patients with serous retinal detachment (SRD) in comparison with preeclamptic patients without SRD (P < 0.01 in all macular points). CONCLUSIONS Our study showed that choroid tends to be thicker in patients with preeclampsia, with statistical significance only in nasal measures. In patients with SRD, however, choroid is markedly thicker at all points analyzed. From these findings we can hypothesize that preeclampsia can cause a choroidal thickening, which begins in the peripapillary area. As the imbalance increases, the entire choroid becomes thickened.