St George's Church and neighbouring Sarah Trimmer Hall, in Brentford High Street, will be turned into 21 homes under plans approved on February 26 by Hounslow Council's planning committee.
The church, built in 1886, had lain empty since the Musical Museum moved to a new purpose-built home down the road in 2007.
Developers had previously applied to demolish the church and neighbouring hall, formerly home to one of the country's oldest Sunday schools, only for that scheme to be defeated in 2004 following a local campaign.
But new developer IDM Properties plans to preserve both buildings, under similar plans to those which were approved in 2009 but fell by the wayside due to the financial downturn.
A chimney stack will be removed and some external walls will go, along with the more modern kitchen extension to the old school hall, but the building's external appearance will be mostly unchanged.
A number of memorial stones and stained glass windows, meanwhile, are set to be removed and preserved in the nearby London Museum of Water & Steam.
Local historian Andrea Cameron said she was "very pleased" to hear an important part of Brentford's heritage would be preserved for future generations.
Ms Cameron told getwestlondon the site was originally home to a chapel, built in the 1780s by the Trimmer family, who owned a local brick works, and the church was later created to serve the population of Old Brentford.
She added that Queen Charlotte, the wife of George III, had been an "unofficial patron" of the school, named after its founder, as she spent a lot of time across the river at Kew Gardens and took a keen interest in efforts to educate Brentford's poor.
Developer Ballymore plans to renovate St Lawrence's Church, further west along the High Street, where the tower dates back to the 15th century, and turn it into a gym.
The conversion would be part of a riverside development including nearly 900 homes, the first phase of which was approved last November.