The English actor, who starred as the titular boy wizard in the beloved film series, made the comments during a BBC documentary marking 20 years since Harry Potter And The Philosopher’s Stone, the first movie in the series, was released in cinemas worldwide.
Rowling, who lives in Edinburgh, has expanded the Potter universe to include the Fantastic Beasts film series, and Radcliffe said “it would be very difficult for anything to happen in the Harry Potter world without her involvement really, and (have) it feel like the same world”.
The 32-year-old continued: “Jo really cares about the people that she writes for. She cares about the people she writes and the people she writes for.
“And it is lovely that she has chosen to expand the world in so many different ways because there is such a hunger for that.
“She is an immensely intelligent, funny, kind human being and I think that obviously comes across in her writing.”
Harry Potter And The Philosopher’s Stone was released in 2001 and propelled Radcliffe, Emma Watson and Rupert Grint to global fame.
The franchise wrapped up in 2011.
Radcliffe also spoke of his joy that many people watch the Harry Potter films when they are “hungover and feeling really crappy about themselves”.
He said: “The time in most people’s lives when they discovered it meant that it has an incredibly important place in a lot people’s childhoods, and they still feel very protective over it.
“One of my favourite fates that we could never have ever imagined for the Harry Potter films but that I have been told by several friends is that they are fantastic when people are hungover and feeling really crappy about themselves.
“They will just watch back-to-back a few movies and it just takes them to a place of warmth and comfort.
“That is so lovely to me. That is the real world effect that a film can have on someone’s life. I think that is great.”