Understanding the crosstalk between synoviocytes and macrophages is very important for the development of strategies to regulate inflammatory responses in an inflamed synovium. Simultaneous regulation of the pro- and anti-inflammatory responses of synoviocytes and macrophages (repolarization) is critical for the treatment of arthritis. Thus, the immune regulatory functions of an ideal nanodrug should not only decrease the pro-inflammatory response but also effectively increase the anti-inflammatory response. In this study, crosstalk between synoviocytes and macrophages was found to be significantly involved in the activation and deactivation of inflammatory responses in the synovium. Interestingly, a developed triamcinolone–gold nanoparticle (Triam-AuNP) complex both decreased the pro-inflammatory responses and increased the anti-inflammatory responses of fibroblast-like synoviocytes (FLSs) and macrophages via repolarization of macrophages from the M1 to the M2 phenotype. In contrast, triamcinolone alone only decreased the pro-inflammatory responses of FLSs and macrophages without upregulating their anti-inflammatory responses. In vitro (human), ex vivo (human), and in vivo (mouse) analyses clearly indicated that Triam-AuNPs effectively regulated the expression of both pro- and anti-inflammatory cytokines in FLSs and effectively repolarized activity of macrophages in the inflamed synovium. Furthermore, Triam-AuNPs significantly promoted cartilage regeneration, whereas triamcinolone alone did not induce either FLS anti-inflammatory activity or macrophage repolarization.