Main •
Hwang Jung-eum as Kim Hye-jin / Jackson •
Jung Da-bin as young Hye-jin :An intern in the administration section before being appointed as junior editor. She used to be a beautiful, wealthy, and smart girl, but lost everything. Embarrassed at her failures in life, she asked her best friend Ha-ri, to meet with her first love Sung-joon, using her name. She thought that would be the end of her fate with Sung-joon, but turns out it's only the beginning of her nightmare, as he then becomes her boss. Despite the misfortunes, she still strives to do her best. •
Park Seo-joon as Ji Sung-joon •
Yang Han-yeol as young Sung-joon :The youngest deputy chief editor in Korea. Stubborn and arrogant but also brilliant in his work. Unlike Hye-jin, he was unattractive and shy but grows up to become handsome and successful. Immediately after returning to Korea, he contacted his first love, Hye-jin. He ends up falling for her even when he didn't recognize that she was his childhood friend and first love. •
Go Joon-hee as Min Ha-ri • Lee Ja-in as young Ha-ri :A hotelier. She is Hye-jin's best friend and roommate. A beautiful and stylish woman with good personality. While continuing to pretend to be Hye-jin, she ends up falling for Sung-joon. Fearing that her relationship with her best friend might be compromised, she tries several times to tell him the truth only to fail in the end and having Sung-joon find out first. •
Choi Si-won as Kim Shin-hyuk / Ten / David Joseph :A senior Feature editor. He is generally a free-spirited, fair, and straightforward man but with mysterious identity (later found out to be the Korean writer, Ten). He is Hye-jin's direct supervisor at work, and they developed a close relationship. He ends up falling for her even before her beauty transformation. He finds out about her relationship with Sung-joon one day when she was drunk.
Supporting Hye-jin's family • Park Choong-sun as Kim Jong-seob, Hye-jin's father who is currently running a small printing house. •
Lee Il-hwa as Han Jung-hye, Hye-jin's mother who also treats Ha-ri like her own daughter too. •
Jung Da-bin as Kim Hye-rin, Hye-jin's younger sister who often prefers Ha-ri as her own sister instead of Hye-jin.
Ha-ri's family •
Yoon Yoo-sun as Cha Hye-jung, Ha-ri's birth mother and Jung-hye's friend. •
Lee Byung-joon as Min Yong-gil, Ha-ri's father •
Seo Jeong-yeon as Na Ji-seon, Ha-ri's stepmother
People in The Most •
Hwang Seok-jeong as Kim Ra-ra :The chief editor who is very fashionable and later found out that she is the chairman's younger sister. She speaks English, Korean, Italian, French and Spanish. •
Shin Dong-mi as Cha Joo-young :Head of the Editing team and director of the Fashion team who is so dedicated to her work. She speaks on behalf of Hye-jin during her initial days and later becomes the deputy chief editor. •
Ahn Se-ha as Kim Poong-ho :A lazy and untidy Feature director who orders his junior coworkers around. It is revealed later that he is the Jinsung Magazine CEO's son and eventually becomes the Vice President. •
Shin Hye-sun as Han Seol :An assistant of the Beauty team who finds out about the fact that the chairman's son is one of her co-workers and sets out to become his love interest. She then dates Joon-woo and eventually falls for his friendly charms. •
Park Yu-hwan as Kim Joon-woo :A cute and kind assistant of the Fashion team who had feelings for Han Seol from the day when she mistakes him as the chairman's son and reciprocates his feelings. He always respects his co-workers and it is later revealed that his parent is the owner of a laundry place. • Kang Soo-jin as Joo Ah-reum :The editor of the Beauty team who is getting married. •
Cha Jung-won as Jung Sun-min • Bae Min-jung as Park Yi-kyung •
Kim Jung-heon as Se-hoon • Im Ji-hyun as Lee Eun-young
People in Jinsung Magazine • Kim Ha-kyoon as Boo Joong-man :Head of the Management team who encourages Hye-jin when she gets transfer to the editing team. • Jo Chang-geun as Kwang-hee, an employee of the Management team. • Jin Hye-won as Lee Seul-bi, an employee of the Management team.
Special appearances •
Im Kang-sung as Ha-ri's date •
Kim Sung-oh as the man at pub (ep. 3) •
Hwang Seok-jeong as the
ajumma in the restaurant on (ep. 7) •
Kim Je-dong as
The Most 20th Anniversary's party MC (ep. 9) •
Lee Joon-gi as the guest for
The Most 20th Anniversary (ep. 9) •
Seo In-guk as the guest for
The Most 20th Anniversary (ep. 9) •
Uee as the guest for
The Most 20th Anniversary (ep. 9) •
Park Hyung-sik as the guest for
The Most 20th Anniversary (ep. 9) • as interviewee for Editor Kim (ep. 11) • Kim Bo-min as Ji Yeon-woo, Sung-joon and Hye-jin's daughter (ep. 16) ==Production==