"I am. I am an alcoholic. It took me a long time to admit that to myself," she told George Stephanopoulos of "Good Morning America."
ABC News confirmed last fall that Vargas, 51, was admitted to a rehab center for alcoholism. She said her drinking had become a "staggering burden to walk around with."
"You become so isolated with the secret and so lonely because you can't tell anyone what's happening," she said.
Vargas revealed that she's had panic attacks since she was a child, when her father left to serve in the Vietnam War.
"I had panic attacks every single day when my mom would leave for work," she said, adding that the panic attacks continued into her adulthood. "I dealt with that anxiety and with the stress that the anxiety brought by starting to drink."
Vargas finally recognized that she needed help when she went to a "20/20" shoot and realized she was "in no shape to do that interview." Vargas is now in Alcoholics Anonymous and said she was proud she confronted her problem.
"I have a sponsor. I have great, great friends who I love and who love me," Vargas said.
She says she's ready to return to "20/20" on Friday night. When Stephanopoulos asked how she knew, she responded, "It's a psychic change, I think. I mean, it's learning to accept that I'm human. That there's nothing wrong with failing, that there's nothing wrong with feeling anxiety."
ABC News contributed to this report.