Kang Ji-hwan started as a musical theater actor in 2002 before expanding his acting career to TV and film. In 2005, he shot to fame after playing his first onscreen leading role in the MBC series Be Strong, Geum-soon! He received an Excellence Award at the 2005 MBC Drama Awards and also scored a Best New Actor nomination at the 42nd Baeksang Arts Awards for his performance in the series. In 2007 and 2008, Kang Ji-hwan led the cast of two successful KBS2 dramas, namely Capital Scandal and Hong Gil-dong. His work in the latter won him the Most Popular Actor for TV award at the 44th Baeksang Arts Awards. In 2008, he starred in the movie Rough Cut, in which he collected several acting recognitions including Best New Actor at the 45th Baeksang Arts Awards. In 2009, he headlined the hit romantic action comedy film My Girlfriend Is an Agent, opposite Kim Ha-neul. He was named Best New Actor at the 46th Grand Bell Awards for his work in the movie.

In 2010 and 2012, Kang Ji-hwan got involved in contract disputes with his former talent management agencies Jambo Entertainment and S-Plus Entertainment, respectively. On July 9, 2019, Kang Ji-hwan was arrested over sexual allegations made against him by two female employees of a subcontracting company. He admitted to the charges. This resulted in the termination of his exclusive contract with his agency Huayi Brothers. On December 5, 2019, he was sentenced to two years and six months imprisonment suspended for three years of probation after being found guilty.