Osteolytic diseases are typified by over-enhanced formation and resorbing function of osteoclasts and have a major impact on human health. Inhibition of osteoclastic differentiation and function is a key strategy for clinical therapy of osteolytic conditions. Maackiain is a natural compound extracted from Sophora flavescens, which has been applied to anti-allergic and anti-tumour treatments. The present results showed that Maackiain could restrain receptor activator of nuclear factor-κB ligand (RANKL)-stimulated osteoclast formation and hydroxyapatite resorption dose-dependently, and interrupt the structures of F-actin belts in the mature osteoclasts. It also repressed the expressions of osteoclast-specific genes and proteins. Furthermore, Maackiain could inhibit RANKL-stimulated NF-κB and calcium signalling pathways, and dampen Nuclear factor of activated T cell cytoplasmic 1 activity, protein expression and translocation into the nucleus. These results revealed that Maackiain may have a potential therapeutic effect on osteoclast-related disorders.