The couple have been together for about 2 1/2 years.
Although Brown has four other children from previous relationships, this will be his first with Etheridge. He was previously married to singer Whitney Houston for 14 years and they have one daughter together, 15-year-old Bobbi Kristina. Brown and Houston, who have both battled addictions to drugs in the past, ended their stormy relationship in 2006.
"I'm really excited about my new addition to my family," Brown told People magazine.
"We're excited because he's in a good place -- he's sober and he's very happy," Brown's lawyer, Phaedra Parks, told the celebrity publication. "And I'm happy for Alicia and Bobby, as well."
Brown's, agent, Ravi Dabiesingh also confirmed the happy news to Usmagazine.com.
"Yes, Bobby is expecting his fifth child from Alicia," Dabiesingh said. "There aren't too many details out there right now, but we do know he is very excited, as Bobby is big on family. The sex of the baby is not known yet, and we can confirm she is four months along."