The Ras association domain family (RASSF) encodes several members with tumor-suppressive potentials. We aimed to investigate the biological function and clinical implication of RASSF10 in gastric cancer (GC). We found that RASSF10 was silenced in six of seven GC cell lines and in primary GC tissues, but was highly expressed in normal gastric tissues. The silence of RASSAF10 was mediated by promoter methylation as evaluated by bisulfite genomic sequencing. RASSF10 expression could be restored by demethylation treatment. A negative correlation between methylation and mRNA expression of RASSF10 was observed in 223 gastric samples of The Cancer Genome Atlas study (P<0.0001). Re-expression of RASSF10 in GC cell lines (AGS and MKN45) significantly suppressed cell viability, colony formation, migration and invasion, reduced cells in S phase, accumulated cells in G2 phase and induced cell apoptosis in vitro, and inhibited tumorigenicity in nude mice. These were confirmed by decreased expression of proliferation markers (proliferating cell nuclear antigen, p-CDC2 and p-CDC25) and increased apoptotic cascades (cleaved caspases-9, -8, -3 and cleaved poly (ADP-ribose) polymerase). Conversely, RASSF10 knockdown in normal gastric cell line yielded an opposing effect. Co-immunoprecipitation combined with mass spectrometry analyses were performed to reveal the downstream effectors of RASSF10. The result revealed that glutathione S-transferase Pi 1 (GSTP1) was a direct cooperator of RASSF10. The tumor-suppressive effect of RASSF10 was partially mediated by cooperating with GSTP1 to deregulate Jun N-terminal kinase (JNK)/c-Jun/AP-1 pathway. Importantly, RASSF10 methylation was detected in 56.6% (98/173) of primary GCs and is an independent risk factor for poor survival of GC patients (P = 0.001). In conclusions, RASSF10 functions as a tumor suppressor by cooperating with GSTP1 to deregulate JNK/c-Jun/AP-1 pathway in GC. Promoter methylation of RASSF10 is associated with poor survival of GC patients.