Considering the intriguing link between career growth and second language (L2), this research aims to promote cross-disciplinary understanding by linking career development with language learning outcomes that are relevant to educational guidance and university support services. In this regard, the influence of career competencies on L2 achievement was explored. In this study, the mediating effects of the dimensions of L2 grit–specifically, perseverance of effort and consistency of interest–were examined between career competencies and L2 achievement scores. The research involved 290 tertiary-level Turkish EFL students who participated voluntarily. Structural equation modelling was employed to test the hypothesised model using RStudio. The findings revealed that career competencies positively and indirectly influenced L2 achievement through perseverance of effort whereas consistency of interest did not serve as a mediator in this relationship. These findings provide career practitioners and language educators with suggestions by highlighting the role of career development in L2 performance.