Personality is shaped not only by individual and social experiences but also by the broader ecological contexts in which populations develop. This exploratory study integrates trait activation, life history, and sexual selection theories into an ecological model to explain cross-national variation in narcissism, Machiavellianism, and psychopathy as measured with the ultra-brief, Dirty Dozen measure. Using standardized data from 48 countries (N = 11,504) and six ecological indicators (i.e., population density, operational sex ratio, life expectancy, natural disasters, disease outbreaks, and income inequality) across three developmental windows, we apply spatial autoregressive models to estimate both direct and spillover effects. We found that harsh or unpredictable ecologies (e.g., male-biased sex ratios, lower survival rates, disaster exposure) were associated with elevated Dark Triad personality traits and these same conditions magnify sex differences, while pathogen prevalence attenuates them. Moreover, neighboring countries' environments influenced focal nations' trait profiles. This work highlights the evolutionary and functional roots of antisocial tendencies at the macro-level by situating the Dark Triad traits within a multi-layered socio-ecological framework.