Published in September, the novel opens with the death of a parish councillor and is based around a local council election.
The best-selling author's first full-length book in five years, it is set in Pagford, a town which appears to be an English idyll but is at war with itself.
Rowling's Harry Potter novels were adapted into blockbuster Hollywood films which launched the careers of Daniel Radcliffe and Emma Watson.
The Edinburgh-based author said: "I'm thrilled the BBC has commissioned The Casual Vacancy. I always felt that, if it were to be adapted, this novel was best suited to television."
BBC1 controller Danny Cohen said: "JK Rowling's story-telling is peerless in its popularity and I am looking forward to collaborating with her."