The new junction 10a of the M20 will serve communities and businesses around Ashford, relieving pressure on the existing junction 10.
Transport secretary Chris Grayling announced the decision in a letter to the Planning Inspectorate, which reviewed the plans last winter.
Work on the improvements will begin early 2018 with Vinci as main contractor and the new junction is expected to open to traffic in 2019.
Highways England regional delivery director Chris Welby-Everard said: “This major new motorway junction is the biggest boost for Ashford since the arrival of international rail services nearly 20 years ago. Junction 10a will unlock job-creating developments in the local area and will take pressure off the existing junction 10. It will bring jobs, better infrastructure for local services and help maintain the quality of life in and around Ashford. Without Junction 10a in place, future economic growth would have been constrained.”