Current research has indicated that M-phase phosphoprotein 8 (MPP8) may affect tumour growth and metastasis, although these relationships have not been explored in human gastric cancer. The present study revealed that MPP8 expression was higher in surgical specimens from patients with gastric cancer (vs. normal adjacent tissues), and that elevated expression was associated with male sex (vs. female sex), intermediate differentiation (vs. poorly differentiated cancer), and later stage (vs. earlier stage). Furthermore, MPP8 overexpression in tumour tissues was marginally associated with a poor prognosis, with a significant relationship between MPP8 overexpression and prognosis among patients with poorly differentiated gastric cancer. Lentivirus delivery of short hairpin RNA targeting MPP8 was also used to explore the function of MPP8 in gastric cancer cells. Inhibition of MPP8 in these cells significantly suppressed proliferation and colony formation, promoted apoptosis, and repressed invasion. Furthermore, silencing of MPP8 remarkably increased the expression of apoptosis-related proteins (p53, Bax, and PARP), and down-regulated Bcl-2 expression. Silencing of MPP8 also decreased the expression of metastasis pathway-related proteins (N-cadherin and vimentin), and as well as the levels of anti-oncogene ZEB1, MET, and KRAS mRNA. These results suggest that MPP8 plays a critical role in regulating gastric cancer apoptosis and metastasis via the p53/Bcl-2 and EMT-related signalling pathways, respectively, which may indicate that MPP8 is a promising target for treating gastric cancer.