An extensive body of research has been done on the links between perfectionism and motivation, yet the underlying mechanisms linking these psychological characteristics have been underexplored. In this study, we used an integrative modelling approach to examine associations between dimensions of perfectionism (i.e. personal standards [PSP] and concerns over mistakes [CMP]), mental toughness (MT) and motivational orientations (i.e. self-determined motivation [SDM] and non-self-determined motivation [NSDM]). Based on a sample of 318 male (n=218) and female (n=100) tennis players (M age =17.61, SD age =2.41), fit indices derived from structural equation modelling supported a partially mediated model. Residual PSP associated positively with MT (β=0.74) and SDM (β=0.40), and negatively with NSDM (β=-0.22). Conversely, residual CMP associated negatively with MT (β=-0.14) and SDM (β=-0.19), and positively with NSDM (β=0.73). Mental toughness was positively associated with SDM (β=0.28), but was unrelated to NSDM (β=0.07). The relationship between residual PSP and SDM was partially mediated by MT (standardised indirect effect: 95% CI=0.19, 0.46). The findings of this study support research linking dimensions of perfectionism with motivational orientations and offer preliminary evidence on the mediating role of MT in the association between these psychological constructs. With emerging research supporting the capacity to develop MT through targeted interventions, the findings are discussed alongside salient implications.