Jenner confirmed the news for the first time and said she's "very excited" to work with Kylie Jenner, 22.
"We're very excited about it," Jenner said. "We've actually not said anything that we're doing it yet, so this is the first time people will know."
"I'm the last sister, or the last family member, I think," she said. "I had a contract before with another makeup company, so now I'm able to do it. I might be wearing some of it ... right now."
Jenner, who was the face of Estée Lauder, shared her excitement about the collaboration.
"I'm excited," she said. "It's cool. I feel like we're really going big because I'm her full-blood. We're taking it seriously."
Kylie Jenner initially made her foray into makeup with her Kylie Lip Kits in 2015 and launched Kylie Cosmetics the next year. In November, she sold her $600 million, majority-ownership stake in the company to Coty.
On Ellen, Jenner also learned and performed a cheerleading routine from the Navarro College cheerleading squad. The squad was the subject of the Netflix docu-series Cheer, released this month.