Obesity has become a major threat to public health and is accompanied by chronic low-grade inflammation, which leads to various pathological developments. Lunasin, a natural seed peptide, exhibits several biological activities, such as anti-carcinogenesis, anti-inflammatory, and antioxidant activities. However, the mechanism of action of lunasin in obesity-related inflammation has not been investigated. The aim of this study was to explore whether lunasin could reduce the inflammation induced by obesity-related mediators in RAW264.7 cells and 3T3-L1 adipocytes and whether it could attenuate the crosstalk between the two cell lines. RAW264.7 cells were cultured in leptin-containing medium, adipocyte-conditioned medium (Ad-CM), or co-cultured with 3T3-L1 cells to mimic the physiology of obesity. The data showed that the secretion of pro-inflammatory cytokine interleukin-1β (IL-1β) was inhibited by lunasin after leptin activation of RAW264.7 cells. In addition, lunasin decreased monocyte chemoattractant protein-1 (MCP-1) and IL-1β secretions in the Ad-CM model. Cytokine MCP-1, IL-6, tumor necrosis factor (TNF)-α, and IL-1β secretions were significantly decreased by leptin or Ad-CM plus lipopolysaccharide stimulation. Subsequently, the co-culture of the two cells refined the direct relation between them, resulting in apparently increased MCP-1, and decreased IL-6 levels after lunasin treatment. In 3T3-L1 adipocytes, lunasin also exhibited anti-inflammatory property by inhibiting MCP-1, plasminogen activator inhibitor-1, and leptin productions stimulated by (TNF)-α, lipopolysaccharide, or RAW264.7 cell-conditioned medium. This result revealed that lunasin acts as a potential anti-inflammatory agent not only in macrophages but also in adipocytes, disrupting the crosstalk between these two cells. Therefore, this study suggests the intake of lunasin from diet or as a supplement, for auxiliary prevention or therapy in obesity-related inflammatory applications.