SPA0355 is a thiourea derivative with antioxidant and anti-inflammatory properties. It inhibits RANKL (receptor activator of nuclear factor κB ligand)-induced osteoclastogenesis in primary bone marrow-derived macrophages and suppresses the activation of MAPKs, Akt, and NF-κB pathways. Furthermore, SPA0355 enhances osteoblast differentiation by increasing alkaline phosphatase activity and mineralized nodule formation. It protects ovariectomized mice from bone loss by stimulating osteoblast differentiation and inhibiting osteoclast resorption, making it a potential candidate for studying postmenopausal osteoporosis.