Harry touched down at London's Heathrow Airport and headed straight to his father at Clarence House in a black car, according to video footage.
"That’s the first time he will have seen his father in any meaningful way, really since the queen’s funeral," Sunday Times royal editor Roya Nikkhah said on TODAY. "He was here for the coronation, but we know he didn’t really see his father."
While Harry will spend time with Charles, he and his brother, Prince William, have no plans to see each other while Harry is in London, a palace source told NBC News.
Harry spoke with his father about the diagnosis and made plans to travel from California to the U.K. to be with him, the office of the Duke and Duchess of Sussex told NBC News on Feb. 5.
"Just seems really sad, hopefully it might heal some of the family rifts, they might all pull together around that," a well-wisher near Buckingham Palace said on TODAY.
Buckingham Palace announced on Feb. 5 that a "separate issue of concern was noted" during Charles' treatment for benign prostate enlargement last month, and that subsequent tests identified a form of cancer.
A spokesperson for the palace confirmed to NBC News that Charles personally told his sons about his diagnosis.
Buckingham Palace did not specify what kind of cancer Charles has, but a palace spokesperson said it is not prostate cancer.
"His Majesty has chosen to share his diagnosis to prevent speculation and in the hope it may assist public understanding for all those around the world who are affected by cancer," the palace said in a statement.
Charles started regular treatments on Feb. 5, and his doctors advised for him to postpone public-facing duties, Buckingham Palace said.
The palace added Charles remains "wholly positive about his treatment and looks forward to returning to full public duty as soon as possible."