The 44-year-old singer, who was diagnosed over a year ago, is now cancer-free.
"Instead of taking five or six of the prescriptions, I decided to go a natural route and smoke marijuana," Etheridge says in an interview to air Sunday on "Dateline NBC" (7 p.m. EDT).
When asked how her doctors reacted, Etheridge says, "Every single one was, `Oh, yeah. That's the best help for the effects of chemotherapy.'"
The singer said she smoked marijuana every day for her pain and symptoms and "the minute I didn't feel it, I stopped."
The use of marijuana with a doctor's recommendation is legal in California and nine other states, but is against federal law. Asked if she was concerned about federal prosecution, Etheridge replied, "No, I didn't worry. But it was worth it."
She recently released a new greatest hits album, "The Road Less Traveled," including the new song "I Run for Life," which is dedicated to the fight against breast cancer.