Rowling's literary agency The Blair Partnership has not yet announced details about the upcoming book, but the author has confirmed her next project is aimed at an older audience.
The author said in a statement: "Although I've enjoyed writing it every bit as much, my next book will be very different to the Harry Potter series, which has been published so brilliantly by [publisher] Bloomsbury and my other publishers around the world.
"The freedom to explore new territory is a gift that Harry's success has brought me, and with that new territory it seemed a logical progression to have a new publisher. I am delighted to have a second publishing home in Little, Brown, and a publishing team that will be a great partner in this new phase of my writing life."
The Blair Partnership has promised that more concrete information about the book will be released "later in the year".
Rowling's Harry Potter books have sold more than 400m copies around the world to become the most successful literary series of all time.
Harry Potter and the Philosopher's Stone - the first book in the Potter franchise – was released in 1997 in the UK and 1998 in the US and became a near-instant hit with children.
Six further Potter adventures followed, with the series eventually adapted to the silver screen with movies starring Daniel Radcliffe, Emma Watson and Rupert Grint.
The final instalment Harry Potter and the Deathly Hallows was released in 2007.
Rowling has expressed mixed feelings on continuing the Harry Potter saga over the years. She famously told Oprah Winfrey in 2010 that future instalments are unlikely, but she wouldn't totally write off the idea of continuing the Potter franchise.
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Watch JK Rowling speak to Digital Spy about Harry Potter below: