Direct attacks on tumour cells with chemotherapeutic drugs have the drawbacks of accelerating tumour metastasis and inducing tumour stem cell phenotypes. Inhibition of tumour-associated fibroblasts, which provide nourishment and support to tumour cells, is a novel and promising anti-tumour strategy. However, effective drugs against tumour-associated fibroblasts are currently lacking. In the present study, we explored the possibility of inhibiting the pathological functions of tumour-associated fibroblasts with triptonide. Paired gastric normal fibroblasts (GNFs) and gastric cancer-associated fibroblasts (GCAFs) were obtained from resected tissues. GCAFs showed higher capacities to induce colony formation, migration, and invasion of gastric cancer cells than GNFs. Triptonide treatment strongly inhibited the colony formation-, migration-, and invasion-promoting capacities of GCAFs. The expression of microRNA-301a was higher and that of microRNA-149 was lower in GCAFs than in GNFs. Triptonide treatment significantly down-regulated microRNA-301a expression and up-regulated microRNA-149 expression in GCAFs. Re-establishment of microRNA expression balance increased the production and secretion of tissue inhibitor of metalloproteinase 2, a tumour suppressive factor, and suppressed the production and secretion of IL-6, an oncogenic factor, in GCAFs. Moreover, triptonide treatment abolished the ability of GCAFs to induce epithelial–mesenchymal transition in gastric cancer cells. These results indicate that triptonide inhibits the malignancy-promoting capacity of GCAFs by correcting abnormalities in microRNA expression. Thus, triptonide is a promisingly therapeutic agent for gastric cancer treatment, and traditional herbs may be a valuable source for developing new drugs that can regulate the tumour microenvironment.