Long non-coding RNAs (lncRNAs) have been shown to have important regulatory roles in cancer biology, and the lncRNA H19 is up-regulated in hypoxic stress and in some tumors. However, the contributions of H19 to gastric cancer remain largely unknown. In this study, we assayed the H19 expression level in gastric cancer tissues by real-time PCR, and defined the biological functions by flow cytometry and RNA immunoprecipitation. We demonstrated that H19 levels were markedly increased in gastric cancer cells and gastric cancer tissues compared with normal controls. Moreover, ectopic expression of H19 increased cell proliferation, whereas H19 siRNA treatment contributed to cell apoptosis in AGS cell line. We further verified that H19 was associated with p53, and that this association resulted in partial p53 inactivation. These data suggest an important role for H19 in the molecular etiology of gastric cancer and potential application of H19 in gastric cancer therapy.