Lee Jin-wook was studying Environmental Engineering at Cheongju University when he dropped out to pursue acting. He began his entertainment career as a print model for Panasonic in 2003, then made his acting debut in My New Boyfriend, a 2004 short film directed by Hur Jin-ho. Roles in television dramas followed, namely: a good-natured stalker in Alone in Love, a baseball player in Smile Again, a private investigator in Someday, an Incheon Airport employee in Air City, a plastic surgeon in Before and After, the president's son in Formidable Rivals, and a newly married chaebol in Glass Castle.

After meeting on the set of Air City in 2007, Lee began dating Actress Choi Ji-woo. The couple broke up in 2011.

Lee then served his two-year mandatory military Service from May 6, 2009 to March 7, 2011 at the Defense Media Agency of the Ministry of National Defense. His comeback project was Myung-wol the Spy, in which he played a North Korean agent.

After playing the heroine's on-and-off boyfriend in I Need Romance 2012, Lee starred in his most high-profile role yet as a TV anchor in the time-traveling romance Nine: Nine Time Travels. The positive reception he gained from Nine led to his being cast in a supporting role in the comedy film Miss Granny, followed by his first major big-screen role in The Target, a remake of French action movie Point Blank.

In May, 2014 Lee reported dating Actress Gong Hyo-jin. However, due to various disparities they broke up after few months of dating.

On 14 July 2016, a woman came forth to sue Lee for rape; she had claimed that Lee followed her home after dinner with mutual friends and raped her. However, Lee denied the claims and countersued her for false accusations. In September 2016, Lee was found not guilty and discharged.

In 2017, Lee was cast in two films; indie film A Winter Guest Scarier than a Tiger; and romance thriller High Society.

In January 2018, Lee returned to the small screen with crime drama Return.