The 40-year-old 'Her' star teamed up with Mercy for Animals, an organisation aiming to prevent animal cruelty, and he has narrated a video detailing allegations against the business, which supplies meat to American retail chain Walmart, reported People magazine.
Phoenix appears in the graphic footage and encourages viewers to join him in taking a stand against cruelty to animals, suggesting they "simply stop eating them".
Since the video went up on the Mercy for Animals website, the actor has received support from an array of stars including Jessica Chastain and Emily Deschanel.