Tesco Metro in Tooley Street opened on Monday with champagne and a presentation of cheques to two Bermondsey charities.
The mid-morning celebration saw store manager Mark Pooley hand over cheques for £500 each to Downside Fisher Youth Club and the Manna Centre.
"This will help us enormously in developing a Friday night youth club," said the club's chief officer Claudia Webbe who also spoke of plans for a film club.
"That will keep young people occupied with more positive things to do at the weekend."
Manna Society administrator Paddy Boyle also welcomed the donation to the centre in Melior Street. "We are struggling to make ends meet," he said. "The day centre is open seven days a week working with homeless people."
Mark Pooley had a very busy time just before the new store was launched as it coincided with the arrival of his second child.
Before handing the day-to-day running to his deputies and returning to his family, Mark said: "My team and I are delighted to be able to offer support to two local charities, both of which provide much needed services for people living in the local community.
"The Manna Centre offers food, clothing, washing facilities and advice to vulnerable people within Southwark whilst Downside Fisher provides social and educational development for vulnerable young people in the local area."
The new store, within the More London development, is below ground with escalator access from Tooley Street. Features include an in-store bakery and a salad and olive bar.
Tesco has invested heavily in promotion for the new store, with vouchers sent to Clubcard holders living in SE1 and Oyster card wallets handed out to commuters at London Bridge Station. There have also been billboard adverts at poster sites in the area.
The store's opening hours are Monday to Saturday 7am to 11pm and Sunday 12 noon to 6pm.