Mesenchymal stem cells have the capacity for self-renewal and under appropriate stimulation give rise to osteogenic, adipogenic, and chondrogenic lineages. To advance the clinical use of stem cell therapy, such as stem cell transplantation, it is important to find substances that promote endogenous stem cell proliferation and differentiation. We investigated whether medicinal herbs have the potential to promote stem cell proliferation and differentiation, using a cell cycle analysis and differentiation assay. We found that Aconiti Lateralis Preparata Radix (ALR) promoted the proliferation rate of mouse bone marrow mesenchymal stem cells (mBMMSCs) up to 122.24% compared to untreated cells. Fluorescence-activated cell sorter analysis showed that the percentage of cells in the G2/M phase increased to 17.33% in ALR-treated cells compared to 5.65% in normal cells. Signaling pathway analysis indicated that this was mediated through the extracellular signal-regulated kinase 1/2 pathway. A differentiation assay showed that ALR induced differentiation of mBMMSCs into an osteogenic lineage 2 weeks after treatment, whereas traditional osteogenic induction medium treatment did not promote differentiation for 3 weeks. This osteogenic differentiation was signaled by the bone morphogenetic protein-2/Smad-dependent Runx2 pathway. We found that ALR could promote mBMMSC proliferation and differentiation into the osteogenic lineage.