The stylish pair are collaborating on their own bespoke line of clothing which will be sold from Paltrow's lifestyle website Goop.
The line, which is called x Goop, will feature investment pieces designed by McCartney and curated by Paltrow.
The Iron Man star told Women's Wear Daily: "I think of myself as a woman who is a lover of beautiful things. I'm very specific about my taste.
"The role I want in a partnership is curating a collection as opposed to taking a designer point of view. I can tweak a blazer and make it the perfect blazer. It's being able to fulfil what my ideal things ought to be."
McCartney added: "I have quite a lot of admiration for her at so many levels and that's a big part of how I design. Her spirit and inner beauty as well as outer beauty are a big inspiration for me."
The collection, which features classic McCartney pieces including a black blazer, black wool trousers and black jeans, will be available from September 12.