Seo was a promising model before he began his acting career, appearing on numerous runways for Korea's leading fashion designers as well as in several foreign designer shows such as Gucci and Tommy Hilfiger.

During his years as a model, he registered himself in acting class to pursue his ultimate goal, to be an actor.

After taking some supporting roles and appearing on TV commercials, he was casted - by everyone's surprise - as a leading actor in the drama "Spring Waltz", the fourth and final feature of the season-themed drama series by director Yoon Sukho.