Archway Campus had been recommended for rejection
Sadiq Khan has called in another student accommodation scheme after Islington council said it would reject the plan.
The London mayor said at the end of last month he will make himself the planning authority for the Baltic Wharf scheme in Paddington.
Plans plans for a 20-storey student accommodation scheme were rejected for the second time by Westminster council in January.
The 605-bedroom proposals by Unite Students and Travis Perkins were rejected due to its height, scale and impact on daylight on nearby residents.
Now he has written to Islington council to say he will also make the decision on the Archway Campus scheme in north London.
This will see the redevelopment of the former Holborn Union Hospital on a 1.5ha site in Archway.
The scheme has faced local opposition, including from Islington North MP and former Labour party leader Jeremy Corbyn, over the height and appearance of the planned 27-storey student tower.
Built as a Victorian workhouse infirmary, the buildings ultimately became a hospital and later a medical teaching campus but have been vacant since 2013.
Under plans brought forward by Seven Capital, three historic buildings would be refurbished and extended, mostly for 87 market sale homes.
Three buildings constructed in the second half of the 20th century would be demolished and replaced with three new blocks comprising 91 affordable homes, of which 58 would be let at social rents.
Grid Architects is responsible for retrofitting and extending the heritage buildings, while Niall McLaughlin Architects has designed the new build masterplan, including the three affordable housing blocks and two student buildings.
Meanwhile, 242 student accommodation studios would be provided in a 27-storey tower which would be 82m in height. There would be another three-storey building constructed to house student amenities.
