Abstract Ovarian cancer is the sixth most prevalent cancer in women and the most lethal of the gynecologic malignancies. Our group has recently shown that STING signaling is often suppressed in a wide variety of cancers, including colorectal carcinoma and melanoma. In this work, we examined the expression and activation of STING pathway in 11 different human ovarian cancer cell lines (CA), generated from the diagnosis of ovarian cancer in varied stages and cultured in vitro. We evaluated STING expression by Western blot in these cell lines and showed that STING is present in 8 of the 11 cell lines. Signaling via STING requires the activation of cGAS synthase enzyme, which was absent in 7 cell lines. In the absence of both STING and cGAS all STING pathway was affected with no IRF-3 and NFκB-p65 translocation and activation. In order to correlate expression levels with STING function in the production of IFN-β, we transfected cells with dsDNA90 to activate STING or with Poly(I:C) for activation via RIG-I. ELISA and Real Time-PCR analyses showed that all 11 CA responded poorly to dsDNA90 stimulation. In contrast, majority of CA were able to produce IFN-β and CXCL10 in response to Poly(I:C), indicating that RIG-I pathway was preserved. Defective production of these cell death control cytokines after DNA stimulus may favor CA proliferation, but also facilitates viral replication and make this CA highly susceptible to HSV1γ34.5 (Herpes simplex virus). Analyzes in vivo by injection of human ovarian cancer cells subcutaneously in Nu/Nu mice followed by HSV1γ34.5 treatments correlates with in vitro findings. The results suggest that STING pathway can be suppressed during ovarian cancer development and these defects let CA more susceptible to oncolytic viral therapy.