Lee Sung-min began his acting career on stage before landing his first silver screen role in the 2001 short film Black & White. He has since become one of the most visible actors in both TV and films in his home country. In 2012, he acted alongside Lee Seon-kyun and Hwang Jung-eum in the hit MBC medical drama Golden Time, which won him Best Actor at the 25th Grimae Awards. In 2014, he was nominated for Best Supporting Actor at the 35th Blue Dragon Film Awards for the period action film Kundo: Age of the Rampant. That same year, he starred in the high-rating tvN workplace drama Misaeng, which scored him the Best Actor trophy at the 51st Baeksang Arts Awards. In 2015, he received a Best Supporting Actor nomination at the 24th Buil Film Awards for the period horror-thriller movie The Piper. In 2018, he joined Hwang Jung-min, Jo Jin-woong, and Joo Ji-hoon in the spy drama film The Spy Gone North, which gave him numerous Best Actor citations including one from the 55th Baeksang Arts Awards. In 2020, he was named Best Supporting Actor at the 25th Chunsa Film Art Awards for the political drama movie The Man Standing Next.

Lee Sung-min and his wife have a daughter together.