The 21-year-old model and the professional makeup artist revealed the news Friday in a clip that played during Good Morning America.
"Everything is about the inner beauty," Upton says regarding cosmetic products. "Bobbi possesses that in her brand."
Brown later reiterated the news in a tweet.
Upton's partnership with the cosmetic line comes a week after she became the new spokesperson for Express. The Sports Illustrated cover girl is also the face of Sam Edelman's digital and print advertising campaign.
Celebrity Couples of 2014 [PHOTOS]