The eyesore opposite Reading train station has been empty since 2010.
Plans to knock the 1970s tower down and replace it with a new 25-storey building were shelved last year.
But developers Landid and Brockton Capital have now been granted planning consent for a major refurbishment scheme.
B&K will extend the current building from 12 to 16 storeys and extend the the existing 147,000 sq ft to approximately 183,000 sq ft of offices and 8,000 sq ft of restaurant/café space.
Trevor Silver, CEO of Landid, said: “Thames Tower is going to appeal to modern businesses who want a lively environment that will attract a young and talented workforce.
“Working with interior architect Penson, we’ll be able to offer fit-out solutions bespoke to each tenant, using the features of the existing structure such as exposed services and soffits to create a visually interesting environment.”
Landid and Brockton Capital have appointed Rider Levett Bucknall to project manage the refurbishment, which is expected to begin in the next couple of months.