NATO will begin moving into its new headquarters in Brussels after several delays caused by technical problems, German news agency dpa reports.
The move of some 4,000 personnel will likely take 12 weeks to complete, officials said.
The new site is near the alliance's existing headquarters, which will continue to be used during the transition period.
NATO said the construction of the new headquarters began with a ground-breaking ceremony in December 2010.
It said the new facility will provide space for 1,500 NATO personnel, 1,700 international military and civilian staff, 600 staff from NATO agencies, and an estimated 500 visitors a day.
The original cost estimate was 750 million euros ($830 million), but actual expenses are currently at 1.17 billion euros ($1.435).
The move had originally been set for January, but it was delayed because of problems related to the new building's IT system.