Ileri Ogunbanwo from Vauxhall Foodbank, which is partnered with the store, joined past Mayor of Southwark Cllr Charlie Smith and Sainsbury's staff to cut the ribbon and welcome customers for the first time last Thursday.
The new 2,500 sq. ft. store is now open from 7am to 11pm seven days a week and is located next door to Pret a Manger, in the former Lendlease sales office.
Customers will soon be able to collect Argos orders from the shop.
The branch has 20 staff, 13 of whom are new to the company.
Patrick Dunne, Sainsbury's property director, said: "We are very pleased to unveil our latest investment in Elephant & Castle, which is creating jobs as well as a convenient new place for local residents and workers to shop.
"The store looks fantastic and I feel sure it will live up to our customers' high expectations of Sainsbury's."
Store manager Adam Spillett said: "It has been an exciting day for me and my team and we look forward to helping our customers find great value, high quality Sainsbury's products in store.
"It's important to us that we play an active role in the local community and it's been great to start getting to know it now our store is open."
Sainsbury's was forced to drop plans for an orange projecting sign outside the store after Southwark Council planners turned down the proposal, saying that the illuminated logo would be out of keeping with the listed Metropolitan Tabernacle building next door.
In 2020 we reported on a petition launched by local residents calling on either Waitrose or M&S to occupy the empty shop unit. More than 300 people signed the petition.