With respect to L2 acquisition, L2 achievement is believed to play an integral role in the process. However, research has demonstrated that due to its multifaceted nature, it can be substantially influenced by an array of once deemed construct-irrelevant factors. Therefore it seems to be imperative to identify such factors in order to develop a deeper understanding of the L2 learning processes. Accordingly, the present study followed a mixed-methods approach to partially fill the gap in the literature, regarding the intricate interactions among L2 grit, FLE, WTC, and L2 achievement, as perceived by Iranian EFL learners. As part of the quantitative phase of the study, 208 Iranian EFL learners were selected via convenience sampling and were asked to complete the L2 grit, FLE, and WTC scales, and to provide their IELTS or TOEFL scores as a measure of their L2 achievement. Thus, multiple linear regression analysis was performed to determine whether the variables could predict participants’ L2 achievement. In light of the results, it was concluded that they were all strong predictors of L2 achievement, with FLE being the strongest. Additionally, SEM was employed to examine the direct and indirect interactions among the study variables. As a result, it appeared that bidirectional relations exist between FLE and WTC, FLE and L2 grit, L2 grit and WTC, as well as directional relations between L2 grit and L2 achievement, WTC and L2 achievement. Furthermore, 20 of the participants participated in a follow-up semi-structured interview. However, despite the discrepancies regarding the interplay of variables, the overall results suggested that L2 grit, FLE, and WTC have a significant effect on L2 development. Thus, the integrated results provided a detailed understanding of the relationship between the study variables, a finding that may be of value to both foreign language educators and learners. The results may also provide the foundation for further research on how so called c
