The purpose of this study was to consider relationships between digit ratio (2D:4D, a putative correlate of prenatal sex steroids) and aggregate personality scores across nations. Differences in national personality scores may be influenced by such factors as prevalence of the parasite Toxoplasma gondii, latitude and economics, and variation in 2D:4D has also been linked to prevalence of T. gondii and to latitude. Here we report associations of mean 2D:4D per country and latitude, gross domestic product (GDP), T. gondii prevalence and personality profiles in 23 nations of an internet study. 2D:4D was not related to latitude or to T. gondii, but was related to GDP (women only). With regard to national personality scores, 2D:4D was not related to masculinity but there were significant positive relationships of 2D:4D with uncertainty avoidance in men and women and with neuroticism in men. Male 2D:4D was significantly related to uncertainty avoidance and neuroticism independent of T. gondii, whereas female 2D:4D was not significantly related to uncertainty avoidance or neuroticism after controlling for the effect of T. gondii and GDP. We conclude that nations with high male 2D:4D (low prenatal testosterone, high prenatal oestrogen) have high scores for uncertainty avoidance and neuroticism.