"The Public Services Network will deliver cost-effective, secure networks to the UK Government and critical national infrastructure," said Phil Naybour, head of Thales UK's security business.
"As one of the world's leading cybersecurity companies, Thales is well-placed to deliver cost-effective, protected networks and secure services through the Public Services Network."
The PSN creates a "network of networks" for the public sector from existing commercial networks to spur efficiencies in procurement through a range of technical and service standards.
The aim is to create an open, collaborative environment for public sector employees and thus improved services.
The contract to Thales UK is for two years, with options for two additional years. No value was disclosed.
Thales said its work will result in best-in-class solutions that are cost-effective and which will improve networks.