Reading ability has had a prominent role in English language education in Taiwan. The comprehension of materials and teacher instruction in English depends on students' English proficiency, and their achievement emotions regarding competence-related activities may influence how they read and complete tasks in English. This study aims to investigate the mediating role of positive and negative achievement emotions in the relationship between instructional clarity, English proficiency, and reading strategies. A questionnaire survey was conducted with 640 university students in Taiwan. The findings corroborated control-value theory. The structural model revealed that the participants' use of reading strategies was strongly influenced by teachers' instructional clarity and students' English reading proficiency. Only positive emotions mediated the relation between instructional clarity, English proficiency, and reading strategies. Negative emotions, though correlated with the two predictors and the reading strategies, did not mediate the relationship between them.