Shoppers will be able to order items from Sainsbury's for delivery in under 30 minutes using the Just Eat app.
The partnership will launch with more than 175 stores by the end of February, with a further roll-out across the country in 2023.
Sainsbury's has its own online delivery service, including its "Chop Chop" service that delivers in 60 minutes.
Just Eat already has partnership deals in Britain with Asda, the UK's No. 3 supermarket group, wholesaler Booker, which is part of market leader Tesco, and fast food group Greggs.
Last week Sainsbury's reported better-than-expected Christmas trading.
According to market researcher NielsenIQ, while online sales rose 2.8% in December, such sales fell to 10.4% of the UK grocery market, versus 11.2% in December 2021.