The aim of present study was to investigate the preferred learning styles of Iranian university students, the differences of learning styles regarding to gender and field of study, and the contribution of learning styles as predictors of the students' academic performance. Using convenience sampling method, 982 students (572 female, 410 male) were selected and were asked to complete the Grasha-Riechmann Student Learning Style Scales (GRSLSS). MANOVA, t-test and multiple regression analysis were used to analyze the data. The results showed that Iranian students prefer dependent, cooperative, and competitive learning styles respectively; Male students preferred avoidant learning style more than the female students, whereas female students preferred dependent, cooperative and collaborative learning styles. The academic performance of students was correlated positively with competitive and cooperative learning styles and negatively with avoidant learning styles. Only avoidant learning style could predict students' academic performance. By understanding the learning styles of students, the educators can use a proper teaching system to meet the students' preferential learning styles.