“Good Morning America” co-host Robin Roberts delivered a powerful message Thursday shortly before she underwent a desperate but successful bone-marrow transplant.

The brave morning-show anchor, who is being treated for a rare blood disorder, offered heartfelt thanks to “GMA” viewers in a taped message.

“This journey is as much about the mind as it is the body,” said Roberts, 51, sitting on a hospital bed and wearing a bright pink baseball cap.

“Your thoughts are so powerful. You’ve got to change the way you think in order to change the way you feel. And let me just say this lastly, I feel the love and I thank you for it.”

The transplant — in which liquefied bone marrow donated by her sister, Sally, was slowly injected through an intravenous drip — took place around 10 a.m. at New York Presbyterian Hospital.

Before the transplant, Roberts’ doctor, Gail Roboz, said the beloved TV personality was bravely handling the grueling situation — which included eight  days of intense chemotherapy to prepare for the treatment.

“Medically speaking, she is doing fantastic,” Roboz said on “GMA.”

But the doctor added sadly, “I think she misses her mother.”

Roberts’ mom, Lucimarian Tolliver Roberts, died Aug. 30 — the day after Robin started her leave from “GMA.”

Roboz said that even reading a few emails and sitting up in bed is exhausting for Roberts, whose 11-day hospital stay has left her weak.

During Thursday’s 90-minute procedure, Roberts was surrounded by her closest friends, family and some co-workers.

“Now, as expected, it is going to be a long waiting game, but we know Robin is going to beat this,” ABC News spokesman Jeffrey Schneider said.

“GMA” weatherman Sam Champion, who visited his pal in the hospital earlier this week, said, “She is in remarkable spirits.”

Roberts is suffering from myelodysplastic syndrome, a disorder spurred by her treatment for breast cancer last year.

According to the National Institutes of Health, approximately 18,000 people develop MDS each year — with several hundred of those cases resulting from cancer treatment.