Pieces are inspired by her upcoming album
The singer tweeted a photograph on Tuesday evening which showed the two women working in what appears to be a design studio.
The caption says it has been “so fun” to “dream up cute stuff” with McCartney, and clarified that the fashion line was inspired by her new album Lover, which will be released on Friday 23 August.
First announced in June, the collaboration will feature limited edition T-shirts, sweatshirts, jackets, bags and a reusable water bottle, with all jersey in the collection made from sustainable organic cotton, in keeping with McCartney's commitment to promoting environmentally responsible fashion.
The line also includes two McCartney pieces: a bomber jacket made from sustainable viscose which will retail at $1,995 (£1,642) and a handbag made from vegan leather for $795 (£654).
In the tweet, Swift included a link to the Stella McCartney website, where fans can register to be notified when the items are available.
Photos of the collection already appear on Swift’s website, and it is set to be available to purchase on Thursday, when Swift will reveal the products on a YouTube Live stream.
The collection is inspired by vintage graffiti, band T-shirts, nostalgic memorabilia and Taylor’s lyrics.
The design is colourful and bright, with some pieces also featuring Swift's cat, which she calls Benjamin Button. The title "Stella McCartney x Taylor Swift" is also prominent on a number of pieces.
Responses to the news have been positive, although some fans alluded to the high price point.
The eponymous fashion brand was launched by McCartney in 2001, and is known for highlighting sustainability and animal rights in its production.