Background Selective serotonin reuptake inhibitors (SSRIs) are commonly prescribed in oncology settings, yet their direct effects on endometrial cancer cell fate and survival signaling remain unclear. This study examined whether clinically aligned, sub-cytotoxic fluoxetine concentrations modulate viability, cell death phenotype, DNA integrity, and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling in endometrial cancer cells.Methods Ishikawa endometrial cancer cells and normal human dermal fibroblasts (HDF) were exposed to fluoxetine (100–300 ng/mL) for 48 hours. Metabolic viability was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell death phenotypes were quantified by annexin V and propidium iodide (PI) staining with flow cytometry. DNA fragmentation was evaluated by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL), and total ERK1/2 and phosphorylated ERK1/2 (pERK1/2) levels were quantified by immunofluorescence.Results Fluoxetine produced a concentration-dependent reduction in metabolic viability in Ishikawa cells, whereas HDF viability was largely preserved across the same dose range. Flow cytometry demonstrated an increase in PI-positive populations with minimal expansion of the early annexin V–positive fraction in Ishikawa cells, consistent with a late-stage or mixed injury phenotype. TUNEL positivity increased dose-dependently in Ishikawa cells but remained low in HDF cells. Fluoxetine markedly reduced pERK1/2 in Ishikawa cells without a comparable change in total ERK1/2.Conclusion Clinically aligned fluoxetine exposure compromises metabolic fitness and genomic integrity in endometrial cancer cells in parallel with suppression of ERK1/2 activation, while normal fibroblasts show relative resistance under the same conditions.