The present study investigates the relationship between online activity completion rate, the grit, the learning style and the achievement of university students in an online TOEIC program. A total of 102 university students participated in an online TOEIC program for 15 weeks as part of their course work. They completed surveys on grit and learning style near the end of the semester. The results show that (a) grit did not significantly influence students’ online activity completion rate nor was there a significance difference in grit between the high and low online activity completion group; (b) learning style also did not have any significant influence on students’ online activity completion rate nor was there a significant difference in the learning styles of high and low online activity completion groups; (c) there was a positive correlation between students' activity completion rate and their achievement in the online TOEIC program. A significant difference in achievement was also found between the high and low online activity completion groups. Implications were discussed in relation to the need to revise the current Grit scale, the role of Korea’s educational system in shaping learning style and the development of an online TOEIC program for learners with different English abilities.