The Davis Cos. of Boston has completed the sale of 24 Farnsworth St. to the Unitarian Universalist Assoc. for $25.5 million.

The church is moving its headquarters from 25 Beacon St. to the six-story brick-and-beam building in the Fort Point neighborhood. The 74,554-square-foot building is 100-percent occupied by the church, which occupies three floors, and a marketing firm.

In preparation for the relocation, the church sold its 39-41 Mount Vernon St. property in August to Mount Vernon Partners LLC for $11.5 million and its 25 Beacon St. property to Sea-Dar Real Estate of Boston for $23.6 million last March.

An investment fund affiliated with Davis Cos. acquired the mortgage on 24 Farnsworth in 2012. Within 10 months after acquiring the building, which was then 85-percent vacant, Davis Cos. brought the building up to full occupancy with leases to Catalina Marketing and the Unitarian church. The developers renovated the building to expose the historic details. The structure contains a 28-space underground parking garage and roof deck.

The church originally signed a 10-year lease with an option to purchase before acquiring the property in the deal that closed last week.

The UUA and its predecessor organizations have been headquartered in Boston since 1825 and occupied the 26 Beacon St. building since 1927.

In announcing the choice of the new headquarters last year, UUA President Peter Morales said the organization was looking for a facility with a collaborative layout and flexible workspaces.