- Park Shin-Hye as Yoo Hye-Jung, from a gangster to a doctor. Due to the abuses she suffered, she is very tough and has a ready-to-fight mentality. With the help of Ji-hong, she transforms into a better person and becomes a doctor.
- Kim Rae-won as Hong Ji-hong, a gifted surgeon with congeniality and popularity. Later becomes a mentor to Hye-Jung which makes her transform to a doctor because of his kindness and guidance.
- Yoon Kyun-sang as Jung Yoon-do, a cool neurosurgeon; as a successor of the country’s leading conglomerate, in order to get rid of his father, he becomes a doctor. He dreams of freedom and a spectacular love.
- Lee Sung-Kyung as Jin Seo-Woo, the main rival to Hye-Jung. Being a former high school classmate of Hye-Jung and a fellow neurosurgeon, her close friends and Ji-hong’s love were all “taken away” by Hye-Jung.
- Kim Min-Seok as Choi Kang-Joo, a neurosurgeon, of the same age as Yoo Hye-Jung and graduated from the top university in the country. He is also a popular blogger who writes about the story of Hye-Jung’s transformation. He later develops a crush on Hye-Jung.
- Kim Young-ae as Hye-Jung’s grandmother,in order to survive, she is willing to sell everything even laughter or heart, because of her son’s mistake, she has to raise Hye-Jung alone with apologetic heart
- Ji Soo as Soo Chul ,he is Yoo Hye-Jung’s First Love.
- Jang Hyun Sung as Kim Tae Ho he is chief of Neurosurgery Department, warmhearted doctor and always take care of patients with sincerity, he is supporter and guidance of Hong Ji Ho.
- Moon Ji In as Sun Hee school principal’s daughter, she refuses her family’s expectation and develop a friendship with problematic Hye-Jung.
Cr. source: Doctors Chinese Wiki