The Dark Triad (DT) involves three closely related personality traits: narcissism, psychopathy and Machiavellianism. Mental toughness (MT) is a multi-facet trait that entails positive psychological resources, which are important across a range of achievement contexts. Research that examined the association between MT and the DT returned mixed findings. The present study aimed at: (1) exploring the association between MT and the DT using a considerable larger sample in comparison to previous studies; (2) investigating whether MT mediates the association between narcissism with psychopathy and Machiavellianism. The mediation model revealed that narcissism exerts significant negative indirect effects on both psychopathy and Machiavellianism, through MT. The implications of these findings for reducing socially undesirable outcomes, often linked to the DT, are discussed.