Oxfam has asked people to call ahead before donating goods, because storage space at its network of charity shops might be limited.
Oxfam stores will begin reopening in England from 15 June.
The charity said it could not yet confirm which stores would open in the first phase, nor how many of them.
However, it said there would be space for social distancing, while staff and volunteers would have the necessary personal protective equipment.
All surfaces, doors and equipment will be regularly cleaned and donated items will be isolated for 72 hours.
Oxfam GB chief executive Danny Sriskandarajah said it was aware that many people had been "busy decluttering under lockdown" and the charity was excited about receiving the resulting donations.
However, the charity also pointed out that with the need to quarantine donated items, storage space could be restricted, so it asked people to call ahead to check beforehand.
All Oxfam shops have been closed since 21 March in response to the coronavirus pandemic.
The move to start reopening them comes after Prime Minister Boris Johnson said that non-essential retailers would be able to reopen in England.
Oxfam shops in Scotland and Wales will remain closed at this stage, as no dates have yet been set for retailers to reopen there.
Oxfam has the third-largest network of charity shops in the UK, with 595 High Street outlets around the country.
Other charities, including British Heart Foundation and Barnardo's, have already announced their own plans to resume operations at a limited number of shops.
Oxfam said it would take time to reopen all English branches, as they varied in size and shape. Arrangements to curb the spread of the virus had to be made on a completely individual, shop-by-shop basis, it said.
Mr Sriskandarajah said: "Our shops are a much-loved part of their communities and, at this difficult time, we can't wait to reopen our doors and reconnect with our supporters and shoppers.
"Our shop staff and volunteers are working hard to make sure we can welcome the public back into Oxfam stores safely."
The charity also said it was appealing for volunteers to help shops get back to business over the summer. Each shop typically has a team of 30 dedicated volunteers and one or two staff, with more than 20,000 volunteers required in all.
The UK's 11,000 charity shops help raise almost £300m for good causes each year and the people who run them are expecting a surge of donations when they open their doors again,
Robin Osterley, chief executive of the Charity Retail Association, said that shops were expecting to be "full to bursting".