BackgroundRecent evidence suggests that accumulation of marrow adipose tissue induced by aberrant lineage allocation of bone marrow-derived mesenchymal stromal cells (BMSCs) contributes to the pathophysiologic processes of osteoporosis. Although master regulators of lineage commitment have been well documented, molecular switches between osteogenesis and adipogenesis are largely unknown.MethodsHSPB7gene expression during osteogenic and adipogenic differentiation of BMSCs was evaluated by qPCR and Western blot analyses. Lentiviral-mediated knockdown or overexpression ofHSPB7and its deletion constructs were used to assess its function. The organization of cytoskeleton was examined by immunofluorescent staining. ALP activity, calcium assay, Alizarin Red S staining and Oil Red O staining were performed in vitro during osteoblast or adipocyte differentiation. SB431542 and Activin A antibody were used to identify the mechanism of Activin A in the regulation of osteogenic differentiation in BMSCs.ResultsIn this study, we identifiedHSPB7capable of oppositely regulating osteogenic and adipogenic differentiation of BMSCs.HSPB7silencing promoted adipogenesis while reducing osteogenic differentiation and mineralization. Conversely, overexpression ofHSPB7strongly enhanced osteogenesis, but no effect was observed on adipogenic differentiation. Deletion of theN-terminal orC-terminal domain ofHSPB7led to decreased osteoblastic potency and mineralization. Mechanistically, our data showed that Activin A is a downstream target participating inHSPB7knockdown-mediated osteogenic inhibition.ConclusionsOur findings suggest thatHSPB7plays a positive role in driving osteoblastic differentiation, and with the capability in maintaining the osteo-adipogenesis balance. It holds great promise as a potential therapeutic target in the treatment of bone metabolic diseases.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13287-023-03361-0.