AIM To explore the let-7a-mediated anti-cancer effect of Yangzheng Sanjie decoction (YZSJD) in gastric cancer (GC) cells. METHODS YZSJD-containing serum (YCS) was prepared using traditional Chinese medicine serum pharmacology methods. After YCS treatment, cell proliferation and apoptosis were assessed by cell counting kit-8 assay and flow cytometry, respectively, and miRNA expression profiles were determined using qPCR arrays. Let-7a expression was examined by in situ hybridization in GC tissues and by qPCR in GC cells. c-Myc protein expression was detected by immunohistochemistry in GC tissues, and by Western blot in cell lines. RESULTS YZSJD significantly inhibited proliferation and induced apoptosis in AGS and HS-746T GC cells. After treatment with YCS, the miRNA expression profiles were altered and the reduced let-7a levels in both cell lines were up-regulated, accompanied by a decrease in c-Myc expression. Moreover, decreased let-7a expression and increased c-Myc expression were observed during the progression of gastric mucosa cancerization. CONCLUSION YZSJD inhibits proliferation and induces apoptosis of GC cells by restoring the aberrant expression of let-7a and c-Myc.