The rocker shared an image of himself wearing a shirt emblazoned with the slogan 'Veganism for everybody'.
He accompanied it with a simple caption, saying: "Go vegan."
Adams regularly posts pro-vegan posts on Instagram - in March he showed off what he described as 'the best food on the planet' -his simple vegan lunch of an avocado garnished with lemon and spice.
At the end of 2017, Adams spoke about his own experiences with a plant-based diet, saying: "I stopped eating animals including fish when I was 28 and I've never looked back. "You can get all the protein you need from plants."
He added: "It's great to see the change that is happening as people embrace a more plant-based diet, but we still have a long way to go. If you want to see your health improve and you care about the planet, go vegan. PS: you can't be a true environmentalist if you eat animals."