The singer/songwriter, who previously slammed the meat and dairy industries for 'torturing animals', posted a video on Instagram - donning an outfit that read 'TICK TOCK'.
'Time is running out'
"TICK TOCK! Our time is running out. The climate crisis is very real," Eilish wrote.
"We need to speak up and demand that our leaders take action. #ClimateStrike #FridaysForFuture@GreenPeace @GretaThunberg."
The star also shared an image from the Global Climate Strike of a protestor's sign that read: "This planet is getting hotter than Billie Eilish."
Global Climate Strike
Yesterday, millions of protestors from more than 150 countries around the world took to the street to participate in the Global Climate Strike - spearheaded by 16-year-old activist Greta Thunberg.
Co-Founder of Plant Based News, Robbie Lockie, who attended the strike in London, said: "The climate strikes are a battle cry from the youth of the 21st Century. They are demanding system-wide change. We can not continue living in a world that places profit above people and the planet.
"This Earth is finite along with every natural resource. If we do not shift towards a sustainable plant-based economy and place a limit on 'infinite growth and profit' there will bee no future. Change must happen NOW!"