The Brethren's Building is a complex of interconnected buildings comprising cells, a Treasury House, and a gallery. The building is situated in the south‑western part of the Kazan Kremlin.
In 1670, a two‑storey building was constructed with square vaulted cells connected by a covered brick gallery. The façades are decorated with cornices and belts, and have arched windows on the first and second storeys. The building was built to accommodate the monks of Saviour's Transfiguration Monastery.
In the 18th century, a three‑storey treasury house with a section of the ancient monastery wall was added on the west side. The arched windows are adorned with architraves, and the façade is decorated with ornamental belts and cornices. The building had a copper roof, which was widely used for roofing at that time.
The L‑shaped Brethren's Building is strengthened by four massive buttresses on its north and west sides.
Today, the building has been restored and is used for administrative purposes.