Mesenchymal stem cells attenuate the severity of lung injury due to their immunomodulatory properties. The effect of bone marrow-derived mesenchymal stem cells on asthma is seldom reported. We have examined the effect of BMSCs on airway inflammation in asthma. Forty female BALB/c mice were equally randomised into PBS group, BMSCs treatment group, BMSCs control group and asthmatic group. Reactivity of the airway to acetylcholine was measured by barometric plethysmography. Cytokine profiles of bronchoalveolar lavage fluid and serum were determined by enzyme-linked immunosorbent assay. Morphometric analysis was done with haematoxylin and periodic-acid Schiff staining. Engraftment of BMSCs in asthmatic mice significantly decreased the number of eosinophils and mononuclear cells in bronchoalveolar lavage fluid and the airway (P < 0.05). Both goblet cell hyperplasia and responsiveness to acetylcholine were significantly reduced in BMSCs treatment groups. Moreover, BMSCs engraftment caused significant increases the ratio of Treg in pulmonary lymph node and interleukin-10 (IL-10) and interleukin-12 levels in BALF and serum. We conclude that BMSCs engraftment ameliorated airway inflammation and improved lung function in asthmatic mouse and the protective effect might be mediated by upregulating Treg and partly involved with increasing IL-10.