Recently, change in the GNG13 expression has been shown to result in multiple congenital malformations and sexual reversal, and it was also found in the brain. The aim of this study was to measure the expression levels in epithelial ovarian cancer (EOC) and breast cancer (BC) and assess their value as a potential prognostic marker. The correlation of GNG13 protein expression was detected by immunohistochemistry (IHC) in 119 EOC and 125 BC tissues. Assessment of the associations between GNG13 levels and various clinicopathological features was identified, the relationship between GNG13 and prognosis in BC and EOC patients was analyzed using online resources of Oncomine and Kaplan-Meier plotter. Protein expression levels of GNG13 were both significantly lower in BC and EOC compared with normal tissues (p<0.0001 and p<0.001, respectively). Among the clinicopathological characteristics of BC, tumor grade (p=0.001) and TNM stage (p=0.001) were significantly associated with low expression of GNG13. While in EOC, low expression of GNG13 was significantly related to FIGO stage (p=0.001), presence of metastasis (p=0.001), and CA125 (p=0.001). Our data suggest that GNG13 expression maybe as a new inhibitor, which can strongly inhibit metastasis and partially attenuates tumor growth in EOC and BC.