Under the £20m deal with Blackpool Council and the £53m agreement with Wyre Council, the firm will replace over 2,900m of the original 1930s seawalls as part of the promenade renewal project.
The scheme will protect over 12,000 properties and local infrastructure from the risk of coastal flooding, Balfour Beatty’s chief executive Andrew McNaughton said in a statement.
Work on both contracts will start this winter, with the Blackpool contract scheduled for completion in summer 2015 and the Wyre work in the summer of 2017.
Both schemes will largely be funded by the Environment Agency, a government body.
They form part of the wider Fylde Peninsula Coastal Programme which aims to protect properties from flooding and regenerate parkland areas.
Balfour Beatty unveiled another new contract win last week - a £64m deal to electrify a western stretch of the Crossrail route.
The firm is already involved in building a new station at Abbey Wood and upgrading above-ground parts of the track.