The decision ends years of waiting for the school rebuild, which was due to go-ahead under Labour BSF building programme, but was scrapped by Coalition education secretary Michael Gove in 2010.
The 1,250-student school will be built on the existing building in three phases to reduce disruption. The first involves building a new sports hall next to the existing sports building.
The second phase will see construction of the main school building. Built across three and four floors, the building will span from the current sports facilities to the area of the school known as A block.
The final phase will see the demolition of the current school building.
Pat Griffin, spokesman for BAM Construction which will carry out the work, said: “It’s a fantastic location and a brilliant school and we really do relish the opportunity to develop something here in Ilfracombe.
BAM is developing a strong presence in the south west after securing several major projects in recent years.