Main •
Lee Jong-suk as Kang Cheol :The lead character of the popular comic series
W. He is the co-CEO of the e-commerce company JN Global, owner of broadcasting channel W, and an Olympic gold medalist in
shooting in his youth. His family was murdered by an elusive murderer, yet Kang Cheol was immediately suspected to be the killer due to his shooting background. After being proven innocent, Kang Cheol seeks vengeance on the murderer through his broadcasting channel W. When he is stabbed on the rooftop of his penthouse by the murderer, he meets Oh Yeon-joo who saves his life and with whom he falls in love. •
Han Hyo-joo as Oh Yeon-joo •
Hyun Seung-min as teenage Yeon-joo •
Park Min-ha as child Yeon-joo :A second-year resident
cardiothoracic surgeon in Myung-sei Hospital. She is the daughter of the Oh Seong-moo, author and
illustrator of the famous webtoon
W. A fan of her father's work, she goes to his studio to investigate his sudden disappearance. There, she is pulled into
W's alternate universe and meets its protagonist Kang Cheol, with whom she eventually falls in love.
Supporting Characters from the webtoon W •
Kim Eui-sung as Han Sang-hoon :The real killer of Kang Cheol's family. His identity is not revealed until much later, and his face resembles the comic series's author Oh Seong-moo. Before Seong-moo gives him a name and face, he mostly appears as a shadowy, faceless human form. •
Jung Yoo-jin as Yoon So-hee :Kang Cheol's long-time secretary and his friend since they were in high school. Her romantic feelings for Kang Cheol are subtly alluded to throughout the series through her actions and behavior around him, which lead to readers' general expectations of their marriage. Originally intended to be the main female character who would later become Kang Cheol's love interest, she is replaced by Yeon-joo when Kang Cheol falls in love with her. •
Lee Tae-hwan as Seo Do-yoon :An apprentice of Seong-moo and confidante of Yeon-joo. •
Nam Gi-ae as Gil Soo-sun :Yeon-joo's mother and Seong-moo's ex-wife. • as Park Min-soo :Cardiothoracic surgeon and Professor at Myung-sei Hospital. He is a passionate fan of
W. •
Kang Ki-young as Kang Suk-beom :Second-year resident cardiothoracic surgeon at Myung-sei Hospital and Yeon-joo's friend. • as Gil Soo-young :Yeon-joo's aunt •
Ryu Hye-rin as Sun-mi :Seung-moo's apprentice • as Yoon-hee :Seung-moo's apprentice
Extended Special appearances • as Kang Yoon – Cheol's father •
Kim Na-woon as Yoon Mi-ho – Cheol's mother (episode 1) •
Seo Shin-ae as Kang Soo-yeon – Cheol's sister (episode 1) •
Choi Min-young as Kang Joon-seok – Cheol's brother (episode 1) •
Hwang Seok-jeong as Webtoon Writer (episode 6) •
Ahn Se-ha as Kim Poong-ho – Yeon-joo's blind date (episode 6) • as Anchorman (episodes 1, 4) • Heo Il-hoo == Episodes ==