The present study's primary aim was to examine the effect of an imbalanced sex ratio on the Dark Triad traits, three types of jealousy, and their relations. For this purpose, data were collected in the Netherlands (n = 297) and Cura'ao (n = 199). Cura'ao is a constituent part of the Netherlands, but has, contrary to the Netherlands, a highly imbalanced sex ratio. We expected the Dark Triad traits to be positively related to anxious and preventive jealousy, but not to reactive jealousy (Hypothesis 1), and, in addition, these relations to be more pronounced in Cura'ao than in the Netherlands (Hypothesis 2). Furthermore, it was expected that Cura'aoan men would score higher on the Dark Triad traits than Dutch men (Hypothesis 3), and that Cura'aoan men and women would, overall, report higher levels of jealousy than Dutch men and women (Hypothesis 4). Results largely supported Hypotheses 1, 2, and 4, but not Hypothesis 3. Results are discussed in relation to the role of sex ratio and the cultural beliefs that may accompany it. The current study's findings may provide new insights into the role of the Dark Triad traits in mating psychology.