The couple will welcome the baby in June, the star's rep confirmed to People.
Loeb and Herskovitz, the Music Production Supervisor for Conan, married on January 31, 2009.
Loeb announced her first pregnancy in September 2009 and gave birth to daughter Lyla Rose in December of the same year.
"I grew up with a big family, so I'm excited for Lyla to have a sibling!" Loeb said.
She has insisted that her family is more important than music and that her life has changed dramatically since becoming a parent.
Watch the video for Lisa Loeb's 'I Do' below: