Under the lease, Dong will be able to carry out geological and environment investigations of an area off the island's coast to establish whether it is suitable for an offshore project.
Dong said the investigations will take a "number of years", after which it could take up an option to extend the lease to cover the lifetime of any project. The inital lease agreement between Dong and the Isle of Man governmnet is seven years.
"We are still very much in the early stages, but this agreement means we can move forward with assessing vital factors, such as wind speeds and ground conditions, critical to determining the viability of the project," said Dong's head of asset management for wind power, Benj Sykes.
Dong said if a project is viable, construction will not begin until after 2020 and the project would be around 700MW.
In November 2014, Dong was selected by the Isle of Man government to develop the site.
The island, which lies between Ireland and Great Britain, is looking to develop offshore energy to export to the UK to help it reach its renewable energy targets and generate income for the government. The island is a British crown dependency.
The IoM owns its territorial waters out to 22km, which covers 4,000 square kilometres. Its shallow waters and close proximity to the UK make offshore wind generation cost effective.
Last year, Dong abandoned its 4.2GW Irish Sea Zone due to "challenging ground conditions". The zone was located just 34km from the Isle of Man.
But a Dong spokesman said the developer was looking at the site independently of the Irish Sea zone.