Lee Sang-yub debuted as an actor in 2007 through the KBS2 series A Happy Woman. In 2012, he appeared in the KBS2 melodrama Nice Guy, which scored him a Best Supporting Actor nomination at the KBS Drama Awards. In 2013, he was named Best New Actor at the MBC Drama Awards for his performance in the weekend series A Little Love Never Hurts. In 2017, he joined the main cast of the SBS drama While You Were Sleeping, which earned him an Excellence Award at the SBS Drama Awards. In 2019, he acted alongside Park Ha-sun in Channel A’s Weekday Afternoon Lovers. In 2020, he starred in the KBS2 family series Once Again, which won him several recognitions including an Excellence Award at the KBS Drama Awards. In 2021, he took home another Excellence Award at the MBC Drama Awards for the workplace drama On the Verge of Insanity.

Lee Sang-yub attended Hanyang University. He served as an active-duty soldier from 2009 to 2011 for his mandatory conscription. He is the only grandson of the late former Dongkuk Steel chairman Kim Jong-jin. He previously dated actress Gong Hyun-joo.