The vacant block known as Empire House overlooks Chiswick High Road and will be revamped and extended to provide 137 homes.
The deal was negotiated during lockdown and is one of the largest residential transactions to take place since the start of the coronavirus pandemic.
Great Marlborough Estates will create 66 in the block, while on adjacent land it will build 67 apartments and four town houses.
In line with changing consumer tastes post-lockdown, each home will benefit from private outdoor space in the form of either a balcony or garden.
Generous amenity space will include roof terraces and a new facade.
At ground level, 9,000 sq ft of retail and leisure space will be created.
Grant Lipton, co-founder of Great Marlborough Estates, said: “While Covid-19 has undoubtedly created some uncertainty, we remain committed to the long-term outlook for London and the capital’s property market thanks to strong underlying fundamentals.
“Acquiring this site in Chiswick marks a significant milestone for Great Marlborough Estates, further expanding our portfolio.”