Nam Sang-mi was working in a Lotteria restaurant near Hanyang University in the fall of 2001 when someone posted her personal photos on the internet.

She made her debut in the 2003 melodrama series Love Letter, and began her acting career by taking small roles in films, TV dramas, and commercials.

[4] In 2008, Nam starred as an aspiring food columnist in Gourmet, a hit series based on Huh Young-man's manhwa Sikgaek.

[5] Nam said regarding her role in horror film Possessed (2009), "The moment I read the script, I wanted this part badly.

[10] In 2014, Nam reunited with Time Between Dog and Wolf costar Lee Joon-gi in the period drama Gunman in Joseon.