PG Tips is to remove plastic from all of its tea bags by the end of the year after more than 200,000 people signed an online petition.
The Unilever-owned brand said its tea bags will be made from a new plant-based material that is 100% renewable and biodegradable to help reduce the environmental impact of the products.
Tea bags are often sealed shut with the heat-resistant plastic polypropylene.
Unilever said its replacement material is made from corn starch and is fully biodegradable.
The first bags with the material will go on sale next week.
Noel Clarke, vice president of refreshment at Unilever, said: "Tea is the most consumed beverage after water in the UK with nine billion PG Tips tea bags made every year and, after 85 years of making PG Tips, we have a great understanding on how Brits love their tea.
"The new 100% plant-based material we're moving to is an innovation based on cutting-edge science and technology and we're all really excited that, starting from now, the PG tips that you know and love will come from 100% plant-based material from a renewable source that's fully biodegradable."
Michael Armitage started the petition, signed by 230,000 people over six months, calling on Unilever to remove the plastic after noticing that "fluff" in his compost heap was coming from tea bags.
He said: "I never believed in a million years there could be plastics used in tea bags. I always assumed they were fully compostable and just made of paper.
"I decided to launch the petition to see if others were as shocked as me, and if we could do anything about it. I couldn't believe it - hundreds of thousands of people signed up to the 38 Degrees petition in just six months.
"People power can make a difference. Now that PG Tips has decided to make the transition, it's time for the other big tea companies to step up like Yorkshire Tea, Tetley and Twinings."