Preeclampsia (PE) is a pregnancy complication characterized by elevated blood pressure, proteinuria, and other laboratory abnormalities. PE affects 2–8% of pregnancies globally and can lead to preterm birth and other complications for the mother and fetus. Successful pregnancy depends on the ability of the mother’s immune system to tolerate the allogeneic fetus. However, in PE, this immune tolerance is exacerbated by inflammation. Transforming growth factor β (TGF-β) is important to retain an immune balance in healthy pregnancy. In PE, TGF-β level is reduced, with an imbalance of the T-cell subset pool to favor inflammation. Omics studies by our group reported an increase in TGF-β signaling when PE-derived placenta mesenchymal stem cells (P-MSCs) were treated with low dose aspirin (ASA). This correlated with increased cycling quiescence and epigenetic changes, resembling healthy P-MSCs. This study tested the hypothesis that ASA could restore the veto property of P-MSCs to mitigate inflammation. ASA (10 mM) treated P-MSCs from PE and healthy placentas increased TGFβ1 and its receptor. The ASA treated MSCs, when added as third-party cells to a one-way mixed lymphocyte reaction, suppressed T-cell proliferation. Prediction studies with omics data indicated that ASA-mediated TGFβ signaling could explain ASA-induced blunting of cell apoptosis. Together, the findings support ASA-mediated expression of TGFβ1 and its receptor on P-MSCs from PE to restore the ability to be licensed as immune suppressor to mitigate PE inflammation. The findings provide new insight into the benefit of ASA treatment for PE.