It will be the first time podiums have been made from recycled materials and organisers say they will need about 45 tonnes of plastic to fashion around 100 podiums for the Games.
Tokyo 2020 CEO Toshiro Muto said the plan would help push a message of sustainability, which organisers want to be a key theme of the Games next year.
"By sending that message to both Japan and the rest of the world, we think this project will have great significance," he told reporters.
Plastic for the project will be gathered at more than 2,000 outlets of a local supermarket chain, where boxes will be set out for Tokyo residents to drop off their recyclable plastic waste.
The project will also use plastic waste that has been collected from the ocean during marine clean-ups.
The 2020 organisers have been keen to promote an eco-friendly message with the Games, including making all the medals from recycled electronic waste.
They solicited waste from the public as well as local Japanese industry and business, collecting 2,700 kgs (about 5,950 pounds) of bronze, 30.3 kgs (67 pounds) of gold and 4,100 kg (about 9,040 pounds) of silver.
And Japanese athletes competing at the Games will also wear an official kit made in part from recycled clothes collected from across the country.