According to a statement, the pair have injected an undisclosed amount of cash into the brand, which is currently preparing to introduce a range of new products in early 2020.
While DeGeneres was a vocal vegan for many years, she revealed at the end of 2018, that she had added some backyard hen's eggs and fish to her mainly plant-based diet.
'Mission behind the products'
"Being kind to one another is not just about people, it extends to animals as well," said DeGeneres.
"Portia and I have been customers of Miyoko's Creamery for several years now, and their cheeses and vegan butter have become staples in our home.
"As we learned more about the mission behind the products and about Miyoko herself, we knew this was a special and exciting company that we wanted to support."
"We are particularly impressed about their holistic perspective to the challenge of moving our society away from animal agriculture," added de Rossi.
"They understand the big picture — that farmers are part of the solution and require our support to transition away from current practices – it takes this holistic view to transition our world to plant-based diets."
'A better world'
Miyoko Schinner, Miyoko's Founder and CEO, said: "We have long admired and appreciated how Ellen DeGeneres and Portia de Rossi have used their platforms to advocate for a better world.
"With their support, Miyoko's Creamery will be better equipped to do our part in helping to further this important shared mission."