The present study examines the association between the General Factor of Personality (GFP) and working memory and its etiology with a behavioral genetic approach. The GFP, which explains the common variance among lower-order personality traits, is considered to reflect social effectiveness. Meanwhile, working memory also plays a significant role in social competence. Hence, we expected a substantial association between the GFP and working memory. A total of 253 Japanese twin pairs (124 monozygotic female; 52 monozygotic male; 28 dizygotic female; 17 dizygotic male; and 32 opposite sex twins) were included in the analyses. Phenotypic analyses confirmed a significant positive correlation between the GFP and working memory. Biometric analysis with a bivariate Cholesky decomposition model showed that the phenotypic correlation derived from additive genetic and non-shared environmental correlations. The present findings are in line with social effectiveness account of the GFP.