"Hi, it's Robin, and I've been waiting 174 days to say this: Good morning, America!" Roberts said with her co-hosts by her side.
Roberts, 52, had been absent from the ABC morning program since August, when she began to prepare for a bone marrow transplant to treat myelodysplastic syndrome, a rare blood disorder.
"I keep pinching myself and I realized that this is real, this is actually happening," she said soon after the introduction.
Throughout the program, Roberts thanked many people who helped with her recovery, including her sister and donor, Sally-Ann. "Welcome Back Robin" video messages from celebrities, including Hillary Clinton and Oprah, were also shown throughout.
"Truly is the dawn of a new day..." Roberts tweeted earlier this morning.
A behind-the-scenes look at Roberts' journey will air on Friday's 20/20 at 10/9c on ABC.
Watch the video of her return: