Background: Subclinical Narcissism (SN) is part of the Dark Triad (DT), which includes also Subclinical Psychopathy (SP) and Machiavellianism. SN comprises facets retained from the clinical syndrome, such as grandiosity and dominance. Previous cross-sectional and longitudinal research indicates that SN may increase Mental Toughness (MT) resulting in various positive outcomes, including lower levels of psychopathy. Method: The researchers conducted three studies (N = 364, 244 and 144 for Study 1, 2 and 3 respectively) to test if the path model from SN to higher MT predicted lower symptoms of depression (DS). An extension to the model considered Openness to Experience (OE) as a possible mediator. Participants completed self-report measures of SN, MT, OE and DS. In Study 3, participants responded to an additional measure of SN to allow differentiation between grandiose and vulnerable aspects. Results: SN exerted a negative indirect effect on DS through MT across studies; and a negative indirect effect on DS through MT and OE in Study 2. In Study 3, Grandiose SN increased MT contributing to lower DS. Vulnerable SN demonstrated the reverse pattern. MT subfactors of Control and Confidence had a mediating effect across studies. Conclusion: The current findings support the model that SN to MT predicts positive outcomes in various domains, including lower levels of psychiatric symptoms. Exploring the link between SN with prosocial traits can be particularly helpful when seeking to identify and promote SN's adaptive tendencies against symptoms of psychopathology.