We have recently identified that the role of secreted protein acidic and rich in cysteine (SPARC) in amelioration of peritoneal ovarian carcinomatosis is mediated, at least in part, through mesothelial cell/lysophosphatidic acid-induced inflammatory response in ovarian cancer cells. The aim of this study was to elucidate the molecular mechanisms of the interactions between tumor cells and the cellular components of the ovarian cancer peritoneal microenvironment, specifically, mesothelial cells and macrophages. We found that SPARC not only significantly reduced macrophage chemoattractant protein-1 production and its macrophage chemotactic effect, but also attenuated the response of ovarian cancer cells to the mitogenic and proinvasive effects of macrophage chemo-attractant protein-1 and decreased macrophage-induced cancer cell invasiveness. Overexpression of SPARC in ovarian cancer cells significantly attenuated macrophage- and mesothelial cell-induced production and activity of interleukin-6, prostanoids (prostaglandins E2 and 8-isoprostanes) as well as matrix metalloproteinases and urokinase plasminogen activator. Moreover, the effects of SPARC overexpression in ovarian cancer cells were mediated, in part, through inhibition of nuclear factor-κB promoter activation. These results indicate, for the first time, that the effects of tumor SPARC as a negative regulator of ovarian cancer are mediated through decreased recruitment of macrophages and downregulation of the associated inflammation.