Previews of the production began on June 7 at the Palace Theatre in London's West End, before it officially opens on June 30. The 50-year-old shared a video and wrote, "Potter fans have always had each other's backs. Today I'm asking you to keep the secrets of Harry Potter and the Cursed Child."
"You've been amazing for years at keeping Harry Potter secrets so you didn't spoil the books for readers who came after you," Ms Rowling said in the video message.
After the first preview on the play, J K Rowling, 50, tweeted on Wednesday:
Harry Potter and the Cursed Child is set 19 years after the happenings of Harry Potter and the Deathly Hallows and is considered as the eighth part to the series of Harry Potter stories. The play is in two halves and is based on a new story by JK Rowling, Jack Thorne and John Tiffany.