LINC00978 expression level was elevated in GC tumour tissues, serum samples and cell lines. The expression level of LINC00978 was significantly correlated with tumour size (P=0.02), lymphatic metastasis (P=0.009) and TNM stage (P=0.009). LINC00978 knockdown inhibited the proliferation of GC cells by suppressing cell cycle progression and inducing apoptosis. LINC00978 knockdown also inhibited the migration and invasion of GC cells. In addition, LINC00978 knockdown inhibited the activation of TGF-B/SMAD signalling pathway and the process of epithelial-mesenchymal transition (EMT) in GC cells. Moreover, the in vivo tumorigenicity of LINC00978 knockdown GC cells in mice was significantly decreased.