Southwark's planning committee has approved proposals to re-clad Guy's Hospital tower and install a light installation at the top.
Councillors voted unanimously in favour of the planning application at Southwark Town Hall on Tuesday night.
Architect Greg Peynore of Peynore and Prasad told the committee that the 1974 tower "is in a very important location in a rapidly changing part of London".
"It's a culturally significant building," he said. "It's been called a Brutalist building and in many ways after 30-something years it may not be reflecting the image that the NHS would want it to.
"Our approach has been both to give this building a new lease of life and also to bring out the best qualities of the existing design.
"It was an important building when it was built. We all have strong views about it and what we've attempted to do is to improve and give strength to its qualities whilst improving it as well."
Mr Peynore said that the recladding project offered the opportunity to tackle the building's "very poor thermal performance".
The communications tower will be clad with so-called 'origami' cladding of folded anodised aluminium which will prevent further deterioration of the tower's concrete facade.
On the main tower, new windows will be installed in front of the existing balconies.
The architect told the the committee that, when the cladding is installed, the tower's energy use for heating and cooling is expected to be reduced by 18.5 per cent.
Installation of the new cladding will start at the top of the tower and work down to the ground to 'seal' the building from outside while hospital operations continue as normal.
There are also plans for an artist-designed light installation at the top of the tower; Guy's & St Thomas' NHS Foundation Trust will have to submit further details of the proposed artwork to the council before it is installed.