Etheridge and her partner, Tammy Lynn Michaels, posted the message, "We are thrilled to announce that Tammy is pregnant, and expecting our twins sometime around this fall."
The couple, who have been together since 2003, revealed that the pregnancy was created with the sperm of an anonymous donor.
The singer is already the mother of two children, Bailey Jean, 9, and Beckett, 7, from a previous relationship.