Bexley Council has moved to the former Woolwich building in Watling Street.
The Civic Offices re-opened on Monday (May 12) and was a flurry of activity.
Staff started to move from the old building in the Broadway last week and all Bexleyheath employees will have relocated by the end of the month. They will be followed by staff based in Slade Green, Welling and Sidcup during June and July.
When the moves are complete, 1,300 office staff currently working from four separate sites around the borough will use the building as their base.
Public reception areas will continue to operate at all the current offices until the last staff move out and each office closes.
The former Woolwich Building Society building was built in 1989 and cost £10.5m. Eleven years later the company was bought by Barclays and the offices became empty.