Middle managers responsible for sustainability operationalize top management decisions on the organization's social and environmental activities. With their focus on sustainability, they could be expected to consider ethical issues particularly well in their decisions and to possess ethical personality traits. While earlier research has focused on top management this paper examines the influence of personality traits of middle managers on their corporate sustainability preferences. Based on a primary survey sample of 204 professionals responsible for sustainability in their company, we study the relationship between dark triad personality traits (Machiavellianism, narcissism, and psychopathy) of sustainability managers and their environmental and social responsibility preferences. The analysis shows that managers who score higher on the dark triad personality scale are less concerned about environmental and social responsibility issues. The business environment, analyzed in a cross-cultural comparison between the United States and Europe, and the organizational context function as a moderator of the influence of personality traits on sustainability preferences. The results suggest that dark triad personality traits should be considered in recruitment and assessment processes of middle managers responsible for corporate sustainability.