Interest in the role of learners’ personality, emotions and the learning environment in foreign language (FL) learning has grown exponentially in the past decade. The introduction of personality psychology in the field of applied linguistics has led to the inclusion of a set of personality dimensions in research designs like resilience and grit, which have been shown to be significant predictors of FL achievement. The abrupt emergence of COVID-19 in 2020 forced universities around the world to move their courses online, which has been named Emergency Remote Teaching. The sudden change in FL learning environment offers a unique opportunity to researchers to investigate whether the relationships between learners’ personality and classroom emotions in traditional ‘in-person’ classes, and the predictors of those emotions, also exist in the new online environments. The present study examined the foreign language classroom anxiety (FLCA) of Chinese secondary students at different instruction levels and its links with learner-internal and external factors, namely general grit and the classroom environment (CE) of the online English classes. A total of 1,526 Chinese secondary students completed an online questionnaire. Pearson correlation analyses and regression analyses revealed that general grit and CE predicted FLCA either independently or jointly. The findings are discussed and interpreted in the light of existing research on person-environment interaction. We identify avenues for further research and propose a number of pedagogical implications for optimizing online FL teaching.