Abstract: To investigate the effects of blocking the signal transducer and activator of transcription 3 ( Stat3 ) on the malignant phenotype of ovarian cancer cell line OV2008. Methods: An ovarian cancer cell line OV2008 sample was infected with adenovirus M4. Reverse transcriptase polymerase chain reaction  and Western blot assays were used to detect the Stat3 mRNA and protein levels, respectively. The effects of blocking Stat3 on cell proliferation, apoptotic rate, and cell invasion capacity were determined by MTT analysis, flow cytometry, and transwell migration assay, respectively. Results: The Stat3 mRNA and protein levels both noticeably decreased in M4-infected OV2008 cells. The proliferation rates of the Stat3-blocked OV2008 cells were significantly slower than those of the control and Ad5/dE1A-infected groups ( P < 0.05 ). The invasion capacity of the Stat3-blocked OV2008 cells was ( 12.64 ± 9.1 ). This value was much lower than those of the control ( 127.7 ± 8.28 ) and Ad5/dE1A-infected groups ( 137.8 ± 9.78 ) ( P < 0.05 ). The apoptosis rate of Stat3-blocked OV2008 cells was ( 65.51 ± 5.78 ). This value was significantly higher than those of the control ( 10.73 ± 4.28 ) and Ad5/dE1A-infected groups ( 12.17 ± 3.87 ) ( P < 0.05 ). Conclusion: Stat3 blockage led to decreased proliferation, increased apoptosis, and decreased invasion capacity in OV2008 cells. Hence, Stat3 may be a new target for ovarian cancer gene therapy.