Ovarian cancer continues to be the most lethal gynecologic malignancy worldwide. IL-27 is a novel member of the IL-12 cytokine family. The aim of this study was to investigate the effects of IL-27 on the ovarian cystadenocarcinoma cell line SKOV3 and determine possible mechanisms underlying its effect. We stably transfected an IL-27 plasmid, empty vector, IL-27 shRNA or negative control into SKOV3 cells. Cell proliferative activity was evaluated using a WST-1 cell proliferation assay kit. Cell viability was quantified by measurements of lactate dehydrogenase release. The mRNA levels of nine genes were tested by q-PCR. Western blotting was used to verify apoptosis and signal pathways. We found that the IL-27 plasmid significantly enhanced cytotoxicity and inhibited the proliferation of SKOV3 cells. Caspase-3 protein was augmented by IL-27 plasmid and abated by IL-27 shRNA. The incremental expression of IL-27 activated the STAT3 pathway and attenuated the Akt pathway. The over-expression of IL-27 could significantly upregulate a series of antitumor cytokines including IL-6, IL-12 and interferon-γ and down-regulate protumor factors such as TLR4 and NF-κB1. Our data show that IL-27 has direct antitumor capacity in ovarian cancer cells via enhancing apoptosis by inducing the STAT3 pathway and restraining the Akt pathway. Précis: IL-27 enhanced the cytotoxicity and suppressed the proliferation of ovarian cancer cells by activating STAT3 and inhibiting the Akt signal pathway. IL-27 plays an important role in antitumor activity against epithelial ovarian cancer. Copyright © 2016. Published by Elsevier Ltd.