JDR will manufacture 242 kilometres of array cables, for two thirds of the 1.2GW, 171-turbine project.
The UK cabling firm will also provide terminations, hang-off arrangements, additional accessories and services to the project, the firm said.
"Hornsea Project One is a major milestone for JDR as it is the largest array cable contract award in our history," said JDR chief operations officer Richard Turner.
JDR is also contract to supply cabling to Dong's 580MW Race Bank site, currently under construction close to the Hornsea Project One site off the UK's east coast.
"We are committed to investing in the UK and it's great to award a significant contract like this to a UK-based company which we know offers high-quality design and reliable delivery in harsh offshore environments," said Dong's Hornsea Project One programme director Duncan Clark.
Delivery will be made in two-batches, with the first set of cables due in Q3 2018, JDR said.
"The offshore wind industry is bringing well over £20 billion in investment to Britain over the course of this decade, creating thousands of jobs. This is happening not only in Hartlepool, but also across the UK, from Liverpool to Lowestoft and from the Isle of Wight to the Isle of Mull," said trade body RenewableUK chief executive Hugh McNeal.
Dong made a final investment decision on the 1.2GW project in February 2016. Hornsea Project 1 is located 120km off England's east coast on site a covering 407 square kilometres, Dong said. The project area is larger than Malta (316 square kilometres).