Lin28 plays important roles in the development, maintenance of pluripotency and progression of various types of cancers. Lin28 represses the biogenesis of let-7 microRNAs and is implicated in both development and tumorigenesis. Oncogenic regulation of let-7 microRNAs has been demonstrated in several human malignancies, yet their correlation with Lin28 has not yet been studied in gastric cancer. Therefore, in the present study, we explored the possible mechanisms involved in the effects by Lin28 on the proliferation, migration, cell cycle arrest and apoptosis in gastric cancer cells via alteration of let-7 miRNA. The expression levels of Lin28 and let-7 were detected by real-time PCR in gastric cancer cell lines in vitro. Lin28 was overexpressed in the BGC-823 cells via lentiviral transfection, and let-7 expression was assessed. Cell proliferation and migration capabilities were investigated by MTT and Transwell assays, while cell cycle distribution and the apoptosis rate were detected using flow cytometry. The expression of Lin28 was moderately expressed in the GES cells while underexpressed in the BGC-823, SGC-7901 and HGC-27 cells. Let-7a miRNA was highly expressed in the GES, BGC-823, SGC-7901 and HGC-27 cells. Overexpression of Lin28 was inversely correlated with the downregulated expression of let-7a, and markedly suppressed the proliferation, migration, cell cycle progression and induced apoptosis in the BGC-823 cells. These findings demonstrated that overexpression of Lin28 can suppress the biological behavior of gastric cancer in vitro, and let-7 miRNA may play an important role in the process. We suggest that Lin28 may be a candidate predictor or an anticancer therapeutic target for gastric cancer patients.