Hae Joo did not grow up with a silver spoon in her mouth. She has had to study and work hard to achieve success as an oceanographer in the male-dominated shipbuilding industry. Kang San, on the other hand, is the son and heir to the major corporation that she works for. Hae Joo’s first love, Chang Hee, also makes something of himself through sheer determination but is still hung up on Hae Joo. Will a family secret change the course of Hae Joo’s life and everything she has worked so hard for?

The drama tells the story of two men who were switched at birth. Chun Dong, born of noble birth, lives his life as a slave while Gwi Dong lives Chun Dong's life as a nobleman. They both fall in love with the same girl, Dong Nyeo.

Oh Je Ro is a musical genius who had always dreamt of learning the piano, but had to work in a piano factory as tuner instead of going to school in order to support his sick father. He had despaired of ever being given a chance to learn and thought the name his father gave him sounded like "Oh, Zero", signifying his lack of hope in the future. This changes when he meets an elementary school teacher, Yoon In Sa, and begins a delicate love story with her.

The drama will be about two men whose fates are crossed from the very first day that they were born. Both men were born in the same hospital. When he was a teenager, Lee Dong Chul witnessed the death of his father. From then on he promised to seek revenge on the man who caused his father's death, Shin Tae Hwan. But unbeknownst to everybody is the fact that Dong Chul's younger brother, Dong Wook, was switched at birth with Tae Hwan's son, Myung Hun. Dong Wook grows up to become a prosecutor and vows to help his brother seek revenge. But what happens when they find out that they're not brothers? What will Dong Chul do when he finds out that his real brother was raised by Shin Tae Hwan and that the brother that was beside him all these years is the son of his enemy?

This drama is a story about love, family, and the realism of people’s dreams! Each character will experience their joy, frustration, and pain at times as they live out their daily lives. Na Dan Poong is a company marketing team leader. Jang Hyun Woo is a plastic surgeon and Baek Ho's friend. Sun Jae is good looking, smart, and makes very good decisions. He has a girlfriend, Ji Young, who he met while they were in college. But to farther his ambitions, he breaks up with Ji Young to marry Bong Soo Ah whose father is the owner of Bonjour Foods.

Choi Jung Soo (Shin Don Wook) was left in an orphnage by his father who could no longer take care of him after his wife left him for another man. He had a bright future in medicine but could ill afford the tuition fee. In despair, he took off to the remote island where his father grew up in the hope that he would find him there. He ended up spending 7 years there working under the guidance of the island's only doctor and became very good at it. But when he saved Yoon Jung Won (Han Ji Hye) who suffered from an acute appendicitis, he became mistaken as a skillful doctor and his life became complicated. YJW was the daughter of the owner of an elite hospital in Seoul and the two began to develope feelings for each other even though she was engaged to be married. He couldn't help falling in love with YJW and began to lie to himself and others about his medical credentials. The higher he rose, the harder he fell. The love that he thought would give him everything turned into poison. He lost his world … except the love of his woman who stood by him no matter what.

Seo Young Ji (Han Ji Hye) was from a poor upbringing and worked as hard as she could to better herself. She went to see a plastic surgeon, hoping that by changing her appearance she would have a better future. The surgeon, a beautfiul young woman called Jeong Ah Mi (Song Seon Mi), asked SYJ for a favor. JAM had been set up on a blind date with Kim Jun Woo (Kim Suk Hoon), but she really had no interest in going. So she asked SYJ to go under false pretense. SYJ agreed to help out with the intention to turn the guy off but the blind date was a hit and the two started dating.

Add to the equation Choi Do Kyeong (Kwon Oh Joong), a poor but ambitious social climber, who would do anything to marry rich. He rejected SYJ as she was poor and did his best to go after JAM.

Secret Lovers is the latest K-drama from MBC, which addresses the most important questions of all - is love reason enough to marry someone, or should you be looking for an equal in both social status and knowledge?