While L2 grit has been increasingly related to language learning outcomes, scant attention has been dedicated to the investigation of the antecedents of L2 grit. To partially address the issue, the present multicultural study models the relationships among L2 grit, academic buoyancy, and self-efficacy. A total of 824 English as a Foreign Language (EFL) students from Iran and China completed three questionnaires. A hypothesised model of the interrelationship among variables was tested using Mplus. According to the final model, L2 grit was significantly influenced by learners' academic buoyancy and self-efficacy. The findings imply that efficacious and buoyant students are more likely to be gritty, and to cultivate L2 grit, the teachers should encourage efficacious and buoyant EFL learners by attending to students' emotional and motivational drives instead of merely cognitive ones. To sustain efforts and interests in language learning, L2 learners need to be more oriented towards belief in personal competencies, positive acceptance of academic life, and autonomy in overcoming difficulties in learning an L2. The findings implied that language teachers might need to better capitalise on learners' self-efficacy and academic buoyancy in order to assist them in improving their L2 grit. Finally, suggestions for future research are offered.