Starring as a Ruth Van Rydock, an old friend of the detective spinster, the 75-year-old will hit the small screen next year in an hour-long episode of the murder-mystery series entitled They Do It With Mirrors.
And it seems the role is a dream come true for the London-born star, who will be appearing in Marple alongside actress Julia McKenzie, who took over the title role earlier this year.
"It has always been Joan's dream to star in Miss Marple," a source close to the award-winning actress says. "She is one of the main characters and has some great scenes."
Other stars set to appear in the new ITV series include Martine McCutcheon, The Bourne Supremacy actor Brian Cox and Wedding Crashers star Jane Seymour.