The job, which will get underway later this year, was being hotly contested by Bam Construct, Farrans and Vinci.
The hospital will be the first in the county to have specialists working around the clock to ensure seriously ill or injured patients get treatment quicker.
As well as a major A&E department, the new hospital, designed by the trust’s clinicians, will include a short-stay paediatric facility and consultant-led maternity unit.
Its innovative design, spread over three floors, includes wards arranged around a central nurses’ station, to enable staff to keep a closer eye on patients.
The new facility is part of the Northumbria Healthcare NHS Foundation Trust’s £200m investment programme to improve healthcare in Northumberland and North Tyneside over the next 10 years.
Gordon Anderson, executive general manager for Lend Lease, said: “This is one of the largest construction projects in the north east at the moment.
“The project recognises our commitment to the building of community facilities for the people of the region.”