Introduction: Dark Triad traits (narcissism, Machiavellianism, psychopathy) are linked to increased psychological distress, including depression, anxiety, and stress. While the underlying mechanisms remain unclear, alexithymia has emerged as a potential risk factor, and mindfulness as a possible resilience factor. This study explores the associations and moderating effects of alexithymia and mindfulness on psychopathology within the Dark Triad spectrum.

Methods: A total of 577 university students completed a cross-sectional online survey (age range 16–50 years, M = 22.73, SD = 6.19, 75.2% female) comprising several questionnaires. Dark Triad traits were assessed using the Dirty Dozen (DD), psychopathology was measured with the Depression Anxiety Stress Scales (DASS-21), alexithymia with the Perth Alexithymia Questionnaire (PAQ), and mindfulness with the Five Facet Mindfulness Questionnaire (FFMQ).

Results: Kendall’s tau-b correlations revealed positive associations between all three Dark Triad traits and facets of psychopathology [r(0.12; 0.18), all p < 0.001]. Regression analyses confirmed specific associations with psychopathology, even when controlling for alexithymia and mindfulness. Moderation analyses were then conducted for significant Dark Triad predictors, focusing on alexithymia and mindfulness. The association between Machiavellianism and both depression and anxiety was moderated by alexithymia (= difficulties appraising negative feelings, p < 0.05), and additionally by mindfulness (= non-judging attitude, p < 0.01) for depression, showing nuanced and complex interaction patterns. Alexithymia regarding negative emotions moderated the psychopathy–stress link (p < 0.05).

Discussion: Small but consistent associations emerged between Dark Triad traits and psychopathology, which were better understood when accounting for gender, alexithymia, and mindfulness. Machiavellianism showed complex, non-linear moderation effects. In contrast, alexithymia regarding negative feelings consistently moderated the link between stress and psychopathy, while narcissism showed no significant associations after controlling for influencing variables.

Conclusion: Dark personality traits are linked to psychological vulnerability, with particularly complex patterns observed for Machiavellianism. Depending on individual levels of alexithymia and mindfulness, these constructs may act as either risk or protective factors. These findings help to uncover the nature of the links between the Dark Triad and psychopathology and reveal novel intervention targets.