The actor auditioned to play late poet Allen Ginsberg back in 2008, but the project stalled while he was wrapping up his final boy wizard movies.
Radcliffe tells the BBC it was "frustrating" to see director John Krokidas struggle to make the biopic, and he was honoured when the filmmaker invited him back onboard when Kill Your Darlings got the green light.
He explains, "Eventually they got it back off the ground and John Krokidas came back to me and offered me the role again. I was tremendously flattered that he did that."
Radcliffe shot the movie with Krokidas in New York, and has branded it the "best experience" of his career so far.
He adds, "We did everything wrong on this movie. You are not supposed to shoot a low budget film as a costume drama and with lots of lavish locations. Somehow we pulled it off, but that's because we were all united in making it happen. Honestly, I think this is the best filming experience I have ever had. I think this is the film where I have developed the most as an actor. It's really special to me, and this is my best work so far - although I'll have to leave it to the critics to decide that."