The Hollywood star was arrested on Friday, reports variety.com.
Jane Fonda's last Fire Drill Friday protest in Washington, D.C., saw the actor march with hundreds, including the likes of Martin Sheen, Maggie Gyllenhaal and Susan Sarandon, and give a speech about the effects of the meat and dairy industries on climate change.
According to US Capitol Police, 147 protesters were arrested in total for the unlawful demonstration.
Since October, Fonda and other actors, including Sam Waterston, Ted Danson, Rosanna Arquette, Sally Field and Catherine Keener, have been arrested for civil disobedience, as they advocated for a Green New Deal, among other demands.
Phoenix attended the protest, standing alongside Fonda onstage to deliver a speech.
In her introduction, Fonda tagged Phoenix "one of the greatest living actors today".
"Something I think isn't oftentimes talked about in the environmental movement or in the conversation about climate change is that the meat and dairy industry is the third leading cause of climate change," he said.
"I think sometimes we wonder what we can do in this fight against climate change and there's something that you can do today, right now, and tomorrow, by making a choice about what you consume."
The remarks came days after Phoenix's acceptance speech for best actor, drama at the 66th Golden Globes Awards, where he praised the Hollywood Foreign Press Association for "recognising and acknowledging the link between animal agriculture and climate change".
"It is a very bold move making tonight plant based. It really sends a powerful message," he said.
The animal rights activist was the one who convinced the Hollywood Foreign Press to implement its first all-vegan menu at the Golden Globes.
Martin Sheen also gave a speech during the protest.
Each week, Fonda uses her Fire Drill Friday protests to advocate for a different cause. She has previously focused on the impact that climate change has on water and women, and has held weekly "teach-ins" with experts to discuss the global issues.
This week, Fonda said the focus was on large financial institutions that allow for the fossil fuel industry, in particular, to thrive.
( With inputs from IANS )