Leighton would acquire all the projects and associated employees in a deal worth A$20m ($21m) while Macmahon retains mining equipment worth A$40m ($42.2m) .
The company carried out a review of its businesses before ariving at a decision to divest the construction arm.
Talking about the recent developments Macmahon chief executive Ross Carroll said that with the sale of construction arm and funding are stragetic to accelerating the mining arm.
"As a result of the review process, the company has made substantial write-downs on construction projects in the first half and has reset its earnings guidance for 2013 financial year net profit after tax to a range of nil to A$25 million," said Carroll.
Macmahon now plans to raise A$80.7m ($85m) in equity in two-for-three, non-renounceable rights to improve its balance sheet and further develop its mining business.
