Extraversion and neuroticism interact to affect subjective well-being (SWB) at the individual level of analysis, so that introverted neurotics tend to be particularly miserable. The goal of this study is to determine if this interaction can also be detected at a national level. Findings based on data from 30 countries confirmed that the interaction between extraversion and neuroticism was an extremely strong predictor of satisfaction with life and affect, and a similar though not significant effect was observed with happiness. Neuroticism lowered satisfaction with life and affect among all nations, but more so among introverted nations than among extraverted ones. These findings further confirm that personality traits can be used to extend our understanding of national differences regarding SWB. They also further validate national SWB scores, as they relate to personality in a complex but theoretically meaningful manner.