Malignant pleural effusion (MPE) carries a grave prognosis with median survival after diagnosis being 5 months. The major causes of MPE are lung, breast, ovary,and gastric cancer. It is still unclear how cancer cells penetrate the pleural mesothelial monolayer and reach the pleural space. In this study we examined the effect of ovarian epithelial cancer cells on a confluent pleural mesothelial cell (PMC) monolayer. We demonstrate that ovarian cancer cells adhere to the mesothelial monolayer in a time-dependent manner and induce PMC barrier dysfunction as evidenced by a drop in electrical resistance on electrical cell substrate impedance-sensing system (ECIS) and increased protein permeability. Barrier dysfunction is attenuated by addition of vascular endothelial growth factor (VEGF) antibody. Significant release of VEOF was noted when ovarian cancer cells were cocultured with PMC. Electron microscopy demonstrated gap formation in PMC monolayer only at the site of cancer cell attachment with surrounding areas remaining confluent.