Twenty gardeners from the private farming company Agripolis will take care of the 14,000m² gardens.
There will be more than 30 species of plants, with 100-plus varieties, from strawberries to aromatic herbs and spinach.
A tonne of vegetables and fruit will be produced every day – and picked at maturity – during high season at the site, near Porte de Versailles.
No pesticides will be used and the plants will grow vertically, without soil.
They will be watered from the top by a sprinkler and the water then collected from under the plants and reused.
Sébastien Martin, Agripolis head of sales and operations, said: “The goal is to produce and distribute locally.
“We will make baskets and sell them to the locals.”
There will also be a bar and a restaurant, offering a panoramic view of Paris, and using seasonal produce from the farm.
Residents will be able to rent a small plot to grow their own vegetables.
Mr Martin said: “The roof of the Parc des Expositions allows us to have a huge surface while staying at the heart of Paris. We are close to everything and there are a lot of people coming here.”
It is not the first urban farm for Agripolis.
The company has five other urban farms in Paris and its outskirts.
It has been working on the latest venture for two years with the help of another gardening company, Cultures en Ville.