The collection will use symbols and images related to Lover and take inspiration from graffiti, vintage band tees, Swift's lyrics from across her career and the singer's cat Benjamin Button.
Items for sale will include organic cotton sweatshirts and t-shirts and a sustainable bomber jacket.
"After Taylor played me the entire album it gave me such incredible inspiration for the collaboration and it really revolved around the music," McCartney said to Vogue.
"What I love is how we really complement each other in what we generate creatively together."
McCartney posted on Instagram Tuesday a photo of herself and Swift looking over designs together.
Swift is set to showcase pieces from the collection on YouTube Thursday at 5 p.m. ET with items going on sale through McCartney's website on Thursday and at a pop-up shop that will appear in New York from Aug. 23-25.
Lover, which includes the singles "You Need to Calm Down," "ME!" featuring Brendon Urie and "Archer," will be released on Friday.
Swift is set to perform on Good Morning America on Thursday and during the 2019 MTV Video Music Awards on Monday.