Balfour beat off competition from Bam Nuttall and Laing O’Rourke for the job which originally had a £70m price tag.
Balfour will deliver a 2.5 mile dual carriageway on the main road link between London and Hastings, together with associated junction and road layout improvements, including two underpasses and an overbridge.
Stephen Tarr, Balfour Beatty Managing Director for Major Projects, said: “Balfour Beatty has a strong track record of delivering major road schemes, both nationally and in the region, on time and to budget.
“Our commitment to building sustainably, engaging with local stakeholders and employing a local supply chain is key to our success and we aim to leave a lasting legacy as a thoughtful contractor behind us.”
Advance work is expected to start this autumn with main construction starting in spring 2015.