The purpose of this study was to investigate the relationship between learning styles and the academic performance of students who attend an English class to learn English as a second language in Iran. A randomly selected group of 488 high school students (248 male and 240 female) participated in this study. They were asked to fill out the Kolb's Learning Styles Inventory to identify four basic learning types: Accommodating, Diverging, Assimilating, and Converging. Academic performance evaluated by achievement test in the English language. The survey results indicated significant relationships between the different learning styles and the performance in an English test, and the performance resulted differently in four groups with different preferred learning styles. The results also indicated gender differences in the performance in English test for convergent and divergent and did not accommodate and assimilate preferred learning styles. These results lead us to conclude that learning styles can be considered as a good predictor of any second language academic performance, and it should be taken into account to enhance students' performances specifically in learning and teaching the second language, and also showed that individual differences in learning styles play an important role in this domain.