The reorganization is to be completed by 2019, a move officials say will save $750 million over 25 years.
The consolidation will also save another $160 million in improvements to existing offices that will no longer be needed.
Most of the amalgamation involves the relocation of 8,500 military and civilian employees to the former Nortel campus buildings, which the Harper government purchased in 2010 following the demise of the technology giant.
The number of National Defence buildings in the capital will shrink to seven from 40, as leases expire.
Neither Defence Minister Rob Nicholson nor Public Works Minister Diane Finley were immediately available for comment.
Published reports earlier this year suggested eavesdropping devices linked to China, left over from the Nortel days, were still embedded in the buildings.
A defence official, who spoke Friday on the condition of anonymity, dismissed the reports. He said military security experts found no such devices during a preliminary sweep.
The military's operational command headquarters, currently located in eastern Ottawa, will remain a separate entity from the consolidated administration centre at the Nortel facility, which is located in the city's south central district.