Despite the rekindled interest in emotions and individual differences in second language acquisition (SLA) under the influence of positive psychology, the interrelationships among regulatory focus, L2 grit and achievement emotions remain under-researched. Drawing on structural equation modeling (SEM) approach, this study aimed to examine the predictive effects of regulatory focus on L2 grit through the mediation of achievement emotions. A total of 1043 non-English major undergraduates from a comprehensive university in central China participated in the study. Data were collected with a questionnaire adapted from three published scales and analyzed using multiple regression and multiple mediation analysis with a 1000-bootstrap method. Results showed that all three psychological constructs under investigation were correlated with each other and regulatory focus had an indirect predictive effect on L2 grit, which was mediated by achievement emotions. As with the mediating effect of achievement emotions, enjoyment and boredom had a partial mediating effect on the relationship between promotion focus and L2 grit, whereas hope and anxiety had a full mediating effect on the relationship between prevention focus and L2 grit. The findings are discussed in relation to the identified mediating mechanism for regulatory focus and L2 grit in boosting L2 learning motivation among Chinese English-as-a-foreign-language (EFL) learners.