Preeclampsia, a multisystem pregnancy-specific hypertensive disorder, results in significant maternal and perinatal morbidity and mortality. This condition is associated with placental histopathological abnormalities and particularly affects the decidual spiral arteries. Reportedly, aspirin prevents preeclampsia, specifically early-onset preeclampsia, although findings in decidual arteries in women treated with aspirin therapy remain unclear. We compared the clinical and histopathological placental findings between women with a history of preeclampsia, who did and did not receive low-dose aspirin therapy (LDA and non-LDA groups, respectively). We identified 26 women with a history of preeclampsia; 9 women received LDA (aspirin ≤ 100 mg/day, initiated at < 16 weeks, LDA group), and 17 women did not receive LDA (non-LDA group). The mean gestational age was higher (36.7 weeks vs. 32.3 weeks, P = 0.0221) and the incidence of preeclampsia was lower (11% vs. 59%, P = 0.0362) in the LDA than in the non-LDA group. Histopathologically, the incidence of decidual arteriopathy, particularly that of fibrinoid necrosis and thrombosis, was lower in the LDA than in the non-LDA group (44% vs. 88%, P = 0.0283). Immunohistologically, endothelial marker (CD31 and CD39) expression was stronger in the LDA than in the non-LDA group. Notably, we observed no significant intergroup differences in inflammatory changes (chronic perivasculitis, protease-activated receptor 1 expression, and CD3-positive cells). This study highlights that LDA inhibits hypertension-induced endothelial injury and thrombosis, and thereby protects maternal placental perfusion and prevents preeclampsia.