Construction company Carillion, which has offices in High Blantyre, Lanarkshire, will start work "imminently" and it will be completed within 12 months.
The improvements will see a 31-mile stretch of line electrified, while Carillion will also lengthen the Cumbernauld station platforms and construct a turnback facility at Springburn.
A spokesman for Network Rail said there would be some disruption to services while work was carried out, but most of the construction would take place overnight and at weekends.
Although on a different railway line from the high-speed route, the project is part of the wider £650m Edinburgh to Glasgow Improvement Programme (EGIP).
David Simpson, Network Rail route managing director for Scotland, said: "This project will create jobs and modernise rail services to Cumbernauld.
"It will also mark the beginning of a transformation of services across the Central Belt."
Scottish Transport Minister Keith Brown said: "The Scottish Government's funding of the electrification of the Cumbernauld line, and our £5billion package of investment over the coming years, demonstrates our continuing commitment to EGIP and the Scottish rail network."