The four-year Water and Environment Management framework will concentrate on flood and coastal erosion work.
Galliford Try has won its place in joint venture with Black & Veatch.
The framework starts next month and has scope for a further two-year extension.
Galliford Try generated £25m in turnover under the final year of the current Agency framework.
Chief Executive Greg Fitzgerald said: “We envisage that the new framework presents a similar or even better business opportunity than we currently have with the Environment Agency.
“This key appointment further enhances our reputation for innovation and engineering expertise within the flood and coastal work sector, and recognises our commitment to providing customers with certainty of delivery and cost within a collaborative working approach.”