The contractor beat Farrans, Robertson and Morrison to the school job with a bid of £23.4m.
Building work on the new school in Laurencekirk is due to start next month, after local councillors approved the project costs and awarded the contract at a meeting of the policy and resources committee.
Lend Lease proposes to award 75% of the work to contractors within a 30-mile radius of Laurencekirk.
The 840-pupil school will feature a range of sports facilities, including a four-court games hall, gym, fitness suite and sports pitches
Vice-chair, Cllr Martin Kitts-Hayes, said: “A replacement Mearns Academy has been part of the council’s long-term asset management strategy and I am pleased to see that the work has been approved.”
Committee members also approved plans for £11.7m of extensions and alterations to Kemnay Academy, to meet projected increases in pupil numbers over the next five years.
The council also approved plans for a new primary school at Kintore, to be built on a site to the east of Midmill Business Park, Kintore, at a cost of £10.4m.