Mental Toughness, Grit, Resilience, and Hardiness (i.e., ‘non-cognitive abilities’), typically affect psychological benefits and performance in a variety of domains, including competitive sport (Denovan et al., 2022). Very little research has investigated these constructs together, which has subsequently limited our understanding of their interrelationships and potential additivity (Denovan et al., 2022; Price, 2019). A better understanding of the similarities and differences among these constructs can help to support the most accurate development of non-cognitive abilities via interventions. The current study explored how Mental Toughness (MTI; Gucciardi et al., 2015), Grit (Grit-O; Duckworth & Quinn, 2009), Resilience (CD-RISC; Connor & Davidson, 2003) and Hardiness (DRS-15; Bartone, 2008) are associated with Sport Perfectionism (SMPS; Dunn et al., 2006) and Passion for Sport (TPS; Vallerand et al., 2003) in a heterogeneous sample of 159 competitive athletes. The results of a stepwise regression analysis revealed that Resilience was a positive predictor of Personal Standards, and Hardiness-Commitment was a negative predictor of Concern Over Mistakes. Mental Toughness and Resilience were both significant predictors of Perceived Coach Pressure; yet Mental Toughness was a negative predictor, while Resilience was positive predictor. The stepwise regression for Passion demonstrated that both Hardiness-Commitment and Hardiness-Control were positive and significant predictors of Harmonious Passion, while only Resilience was a positive predictor of Obsessive Passion. The main results highlight that these four conceptually interrelated constructs are distinct with respect to two factors that are known to influence motivation in sport.