Fashion King tells the story about a young aspiring designer Kang Young-gul (Yoo Ah-in) who has nothing and starts his fashion business as a vendor on Dongdaemun Market. He has never had any goals or dreams for a bright future until he meets Lee Ga-young (Shin Se-kyung) who loses both parents in an accident at a young age and grows up into a smart, determined young woman with a natural talent for designing. After receiving a scholarship to the New York Fashion School, Ga-young travels to America hoping to achieve her dream of becoming a designer.
Meanwhile, Jung Jae-hyuk (Lee Je-hoon) is a second-generation chaebol to a large enterprise that covers construction, distribution, and fashion, while his ex-girlfriend, Choi Anna (Kwon Yuri) now works under a top internationally renowned designer. Gradually, Jung Jae-hyuk loses interest in Choi Anna and sets his sights onto Lee Ga-young. But Ga-young\'s heart is for Young-gul, and Young-gul\'s heart is for Anna, so will this love square ever be settled? And who will win and become Fashion King?