Ennis has been editor of the magazine for ten years. She will stay on through the magazine's forthcoming tenth anniversary and will work on a new look for the title in the new year.
The Now boss previously worked on magazines including Honey, Nova, TV Times and Best, as well as newspapers Today, the Sunday Mirror, the Daily Mail and the Daily Telegraph. She launched Here! with Gruner + Jahr, which was later acquired by IPC and merged into Now.
In recent months IPC has extended the brand across different platforms. Nowmagazine.co.uk launched in August and October saw the launch of a book called Now Celebrity Passions. This week Now has partnered with Sony BMG for The Ultimate Celeb Quiz interactive DVD game.
IPC Connect managing director Evelyn Webster said: "Jane Ennis is responsible for creating the modern mainstream celebrity weekly, and her achievements have been much emulated by her rivals. Her five BSME and PPA awards are testament to her continued drive to constantly set the standard in the weekly sector."
Ennis' replacement has not yet been announced.