The contractor, a joint venture of Farrans Construction and H&J Martin, will start work this month.
The new 1,200-capacity school, which is a replacement for the existing Ellon Academy, is scheduled to be completed by August 2015.
Councillor Martin Kitts-Hayes, vice-chair of Aberdeenshire Council’s policy and resources committee, said: “This project is part of our wider capital works programme which is investing heavily in schools over the coming years to ensure our educational facilities are built and maintained at the highest possible standard.”
FMP director Raymond Millar said: “We are delighted to be included in Aberdeenshire’s capital plan of works and that our first opportunity is the Ellon Academy Community Campus.
“It is an outstanding project in a challenging environment. We recognise that this building project is more than just a school, and we are committed to engaging with the wider community as part of the delivery of this first-class facility.”
Planning permission for the new school was gained in October 2012, and the site at Cromleybank was purchased in January 2013.
Ellon is 16 miles north of Aberdeen.