Background <p>Preeclampsia (PE), a hypertensive disorder of pregnancy, is characterized by impaired trophoblast cell function. The 5-hydroxytryptamine receptor 1D (HTR1D) has been implicated in trophoblast cell regulation, yet its specific role and the underlying molecular mechanisms in preeclampsia remain unclear.</p> Methods <p>Trophoblast cells (HTR-8/SVneo) were exposed to CoCl₂ to mimic an in vitro model of PE. The mRNA levels of HTR1D and RNA binding motif protein 15 (RBM15) were quantified using quantitative real-time polymerase chain reaction, while protein expression of HTR1D, RBM15, and YTH N6-methyladenosine RNA binding protein F2 (YTHDF2) was assessed by western blotting. Functional assays, including cell counting kit-8, 5-Ethynyl-2’-deoxyuridine, transwell, flow cytometry, and caspase-3 activity assays, were employed to evaluate cell viability, proliferation, migration, apoptosis, and oxidative stress. Methylated RNA immunoprecipitation (MeRIP) and RNA immunoprecipitation (RIP) assays were performed to examine the interactions among HTR1D, RBM15, and YTHDF2. The actinomycin D assay was used to assess mRNA stability.</p> Results <p>HTR1D expression was significantly downregulated in PE patients and hypoxia-induced HTR-8/SVneo cells, whereas RBM15 expression was upregulated. Overexpression of HTR1D mitigated hypoxia-induced inhibition of trophoblast proliferation and migration, as well as reduced apoptosis and oxidative stress. RBM15 was found to destabilize HTR1D mRNA in a YTHDF2-dependent manner. Silencing RBM15 enhanced trophoblast proliferation and migration while suppressing apoptosis and oxidative stress by upregulating HTR1D.</p> Conclusion <p>The RBM15/YTHDF2-mediated destabilization of HTR1D mRNA exacerbated hypoxia-induced dysfunction in trophoblast cells associated with PE. These findings highlight the potential of targeting the RBM15/HTR1D axis as a therapeutic strategy for managing PE.</p>