The relationship between grit and success has been investigated extensively in various contexts. However, the association between grit and language performance, especially in a Chinese high school context, remains underexplored. This study investigates grit, the positive emotion of enjoyment, the negative emotion of anxiety, foreign language performance, and how enjoyment and anxiety mediate the relationship between grit and foreign language performance. A questionnaire was administered to 697 Chinese high school students, followed by a language test after 2 weeks. The results showed that more than half of the students had a moderate-high level of grit and foreign language enjoyment and that nearly half of them experienced a low-moderate level of foreign language anxiety. It was also found that grit, foreign language enjoyment, and foreign language performance were positively correlated with each other, and all three variables were negatively correlated with anxiety. Both foreign language enjoyment and foreign language anxiety mediated the relationship between grit and foreign language performance to a significant degree, and the mediating effect of foreign language anxiety was stronger than that of foreign language enjoyment.