The show began strongly two years ago with a peak of almost a million viewers for the launch, but audiences steadily declined to around 200,000 viewers by the time series two finished last December.
"Hex was an exciting, original idea that captured the attention of critics and audiences alike," Sky One controller Richard Woolfe told Broadcast. "We're extremely proud of the series, but feel that it's come to a natural end. I'm confident that the ideas we have in development will have a similar impact when they're broadcast."
The series is the second original commission to be axed by Woolfe in as many weeks, having already ditched long-running football drama Dream Team.