The American-based firm will help HS2 Ltd carry out the next phase of engineering, design and environmental work on the London-to-Birmingham line, the first phase of the project.
Also the delivery partner for the London Olympics, CH2M Hill recently bought UK consultancy Halcrow, which has worked on HS1 and Crossrail. HS2 Ltd said the contract would create about 80 jobs.
CH2M Hill will provide an 80-strong team, mostly project management and engineering specialists, to work alongside HS2 Ltd.
It will co-ordinate the various professional services companies who will carry out all the design, environmental and land referencing work for phase one of the project.
The government gave its backing to the controversial proposals for the first phase of the new high-speed rail network earlier this month.