Introduction: Preeclampsia is a pregnancy-specific complication characterized by hypertension in combination with proteinuria and/or various manifestations of multiple organ failure. It is believed that etiology of preeclampsia lies in dysfunction of the placenta and disorder of the maternal-fetal interactions. In preeclampsia decidual membrane, the maternal part of the placenta which normally supports immunological tolerance of the maternal organism to the semi-allogeneic fetus, becomes a site of inflammation. Methods: The aim of our study was to characterize the phenotype of decidual macrophages and plasma profiles in patients with late- and early-onset preeclampsia as compared with controls (n = 43). Decidual cells were obtained by enzymatic digestion method and characterized by flow cytometry analysis, real-time PCR, bioinformatics analysis, immunohistochemistry, and Western blot. Plasma samples were analyzed by multiplex assay. Results: The number of inflammation-associated CD86+ and CX3CR1+ cells was significantly higher in the early-onset preeclampsia while the portion of CD163+ cells was significantly higher among studied groups. We observed significant increase of endothelin-1 gene expression and a significant decrease in eNOS and GNB3 expression and TGFβ relative protein level in decidual cells of the early-onset preeclampsia samples. We also revealed elevation of pro- and anti-inflammatory cytokines in plasma of preeclampsia groups. Discussion: Our findings reflect profound early-onset preeclampsia-associated alterations in the decidua and emphasize the importance of the decidua as a link in the development of preeclampsia. © 2021 Elsevier Ltd