Oates, a former producer of Radio 4's The Archers, will take up her new position in January when current boss Stuart Blackburn moves to Coronation Street.
The new chief already has experience at Emmerdale as she worked as the programme's story editor from 2010 until earlier this year, when she landed the job of assistant producer at Corrie.
Oates commented: "I always thought I'd love to go back to Emmerdale but I never expected it to happen so quickly. I'm delighted to be Emmerdale's new producer as I'm passionate about the programme and everyone who works on the show.
"The last block of storylines I worked on before my recent move was the 40th birthday week, so I'm very excited to see the stories play out this week and I'll be glued to the live episode."
Oates served as producer of The Archers for seven years from 2003 to 2010. Before that, she worked as researcher and editorial assistant to Germaine Greer.
She continued: "I feel very lucky to be returning to such a wonderfully successful show. I'm in awe of the cast, crew and writing team and it's a privilege to be renewing my working relationship with everyone.
"I've been fortunate since leaving university to work with some inspiring people - Vanessa Whitburn, editor of The Archers, and the inimitable Germaine Greer, and later my friends and colleagues on Emmerdale and Coronation Street.
"They are people who have given me opportunities and looked after me throughout my career, and I will never forget their kindness and enthusiasm."
After taking up her new post in the New Year, Oates will report to John Whiston, ITV's creative director for soaps.
Whiston commented: "Kate swept into Emmerdale a couple of years ago with a deadly combination of determination and brio. She soon proved her worth to the show, working on stories that ranged from the extremely tough to the light and funny.
"It is great that she is ping ponging back over the Pennines from her recent stint on Coronation Street to a show on which, by both inspiration and sheer hard work, she has won herself many admirers.
"I can't think of many people more in tune with the vibrant spirit of modern Emmerdale than Kate. And I can think of even fewer able to keep it that way as it heads into its 40s."
Emmerdale's 40th birthday celebrations will play out all this week on ITV1. Get the Inside Soap magazine on your iPhone or iPad