Amey will maintain the M4 Prince of Wales, M48 Severn and M5 Avonmouth bridges from November.
The contract, worth £16m per year, will see include structural inspections, routine maintenance and major renewal schemes.
Highways England Operations Director Nick Harris said: “Our roads and bridges are among the safest in the world and partnerships like this will help maintain high standards on the three large bridges in the south west.
“By working more closely with our supply chain who carry out maintenance, we will be able to work more effectively, identify innovative ways of working and provide the best possible quality of service to road users.”
Each of the structures has its own unique characteristics and structural complexities.
The M5 Avonmouth Bridge spans 1.4km, the M4 Prince of Wales Bridge comprises three structures, the Avon Viaduct (2.1km), Cable Stay (948m) and Gwent Viaduct (2.1km), while the M48 Severn Bridge, a suspension bridge covers 1.6km of road network and has the second highest tidal range in the world at 14.5m.
Peter Anderson, managing director for Transport Infrastructure at Amey, said: “Amey will bring a wealth of innovative operational solutions and capabilities regarding bridge infrastructure, which has been recognised by Highways England, through our work on the Forth Road Bridge amongst other structures across the UK.
As part of the contract, Amey will become a member of the South West Asset Delivery Community, ensuring the contract provides the best possible value for money and service to its customers through the collaborative network with suppliers and other service delivery partners operating on this contract.