Students act according to their beliefs and mindsets. Being aware of such individual differences can help L2 teachers make sound and evidence-based educational decisions. Having said this, the purpose of the current study was to explore the relationship among language mindset, language proficiency, and anxiety through a path analysis in an EFL context at different proficiency levels. The study involved 500 Iranian English learners in six private language institutes. The instruments used were a modified version of the language mindset, foreign language anxiety, and self-reported proficiency. The path-analytic results revealed that the model with the three variables enjoyed a good fit, confirming an interrelationship among L2 language mindset, anxiety, and proficiency. Furthermore, the study also reported a significant relationship between mindset, anxiety, and language proficiency. Negative attitudes towards learning a foreign language, such as fear of negative evaluation, bad experiences in the classroom, and students' beliefs about their abilities, have a significant association with L2 anxiety. In addition, students with higher levels of proficiency have more positive mindsets and experience less anxiety than their counterparts. We discuss the implications of these findings for EFL learners and teachers.