A considerable amount of research has investigated the separate roles of motivation and identity in language learning. This study aimed to examine these two important constructs jointly by exploring the relationship between motivation, identity processing styles, and English learning among high school students. The hypotheses were empirically tested using questionnaire data collected from 187 Macau high school students. Correlation analysis found that only self-determined motivation was significantly positively related to academic performance in English and that none of the five identity processing styles was relevant. Further hierarchical regression analysis revealed that after controlling for age and gender, identification with commitment and ruminative exploration both negatively predicted English performance. Significant interaction effects were found between exploration in depth and self-determination and between ruminative exploration and self-determined motivation. However, ruminative exploration was the only significant predictor of academic performance when the students had low levels of self-determined motivation.