Bexley Council has announced it will re-open in the former Woolwich building in Bexleyheath on Monday, May 12.
The move has been under discussion for many years and will save the council more than £1.5 million a year.
All of the 1,300 office-based staff - who are currently based at four separate sites around the borough - will move into the building during May, June and July.
It will be the first time the building has been occupied since its closed eight years ago.
Council Leader, Cllr Teresa O’Neill said: "I am very proud that we are close to completing what has been a complicated and challenging project that will benefit local people now and for many years to come.
“We have completed the sale of the sites we are leaving and the ambitious aims we set for ourselves when we started the project have all been met.
“When the move is complete, this will be the first time that all our office-based staff will be working under one roof, with good technology to help them deliver better services and value for money for our residents.
"We’ll also have just one front door – which should make life simpler for our customers and save money running four costly and inefficient old buildings.”
Council telephone numbers, email addresses and online services will not be affected by the move, which has been carefully planned so that services continue with the minimum of disruption.
The cost of buying and refurbishing the offices has been met by the sale of office sites the council no longer needs and is also helping to fund investment in local schools and community facilities.
The project is also freeing up land for the construction of 700 new homes across the borough.
The council’s former offices in Wyncham House, Sidcup have also been leased to a local company.
Staff will move from the current Civic Offices in the Broadway Bexleyheath in May, the Howbury Centre in Slade Green in June and Hillview in Welling and Hadlow Road in Sidcup in July.
The postal address of the Civic Offices will be: London Borough of Bexley, Civic Offices, 2 Watling Street, Bexleyheath, Kent DA6 7AT.
The site of the current Civic Offices has been used continuously as council offices since 1903 – 11 years before the outbreak of the First World War.
The current offices are expected to be demolished in the summer to make way for a new Tesco store.
Council staff working in area focused teams based at Foots Cray, in libraries, children’s centres, at the Youth Advisory Service in the Broadway and Atrium Court in Erith will not be moving. The Council Tax and benefits service based at Erith Town Hall will also not be affected.
For more information about the move visit bexley.gov.uk/wearemoving