The high mortality rate associated with chemoresistance in high-grade serous ovarian cancer (HGSOC) underscores the urgent need for effective treatment strategies. This study explores the role of estrogens in six HGSOC cell lines differing in carboplatin sensitivity, estrogen receptor expression, and the ability to convert estrone sulfate (E1S) into active estrogens. We assessed the effects of the steroid sulfatase (STS) inhibitor STX64 and the estrogen agonists equilin (EQ) and ethinylestradiol (EE2) on cell viability, cell death and migration, as well as their interaction with carboplatin. STX64 IC₅₀ values for cell viability varied widely—from 18.21 µM (COV362) to over 90 µM in most lines. Significant viability reductions generally occurred at ≥ 50 µM, except in Kuramochi cells that were sensitive at 10 µM, and in OVSAHO and OVCAR-4 that responded at ≥ 0.01 µM. At higher concentrations, STX64 reduced viability in all cell lines, including ERα-negative cells. Combination treatment outcomes varied: STX64 reduced carboplatin efficacy in OVSAHO and COV362 but enhanced it in Caov-3. EQ and EE2 decreased viability in several cell lines, except in OVSAHO, where EQ promoted proliferation. Both enhanced the antimigratory effects of carboplatin in cell lines with moderate ESR1:ESR2 ratios. Moreover, STX64 induced apoptosis, carboplatin triggered necrosis, and E1S potentiated both, indicating distinct cell death mechanisms. These findings emphasize the role of estrogen signaling in modulating the chemotherapy response in HGSOC. Although STX64 may not consistently enhance carboplatin effects, its strong pro-apoptotic activity and selective efficacy in ER-positive cells, highlight its promise as a potential standalone or maintenance therapy.