Lee Moo-saeng made his screen debut with a supporting role in the 2005 film See You After School and has since become active in both TV and film. In 2007, he appeared in the MBC medical drama White Tower, which was nominated for Best TV Drama at the 43rd Baeksang Arts Awards. In 2009, he joined the cast of director Lee Yeon-woo’s Running Turtle, which topped the box-office for the first two weekends of its release. In 2019, he acted supporting roles in several television dramas such as tvN’s The Crowned Clown and MBC’s One Spring Night. In 2020, he became part of the main cast of JTBC’s megahit series A Couple’s World. In 2021, he starred alongside Gong Yoo, Bae Doo-na, and Lee Joon in the Netflix sci-fi drama The Silent Sea.

Lee Moo-saeng attended Sejong University.