Kerry county councillors last year contravened their own development plan to allow Mr Brennan to build the park in woodland on the coast, surrounding a protected 19th-century manor house.
Objections were raised with An Bord Pleanala, but these have now been withdrawn.
The "glamping park" is a low density luxury family campsite at the 32-acre lakeside site.
The project includes the installation of 32 tents, 62 recreational vehicle stands, shop and laundry facilities, as well as the renovation of the existing hotel and 12 bedroom suites as well as restoring the manor house to its original design.
Planning permission for the park required contravention of the county development plan, which bans coastline caravan parks.
Mr Brennan said 35 jobs would be safeguarded by the decision and that number will probably be expanded.
"It's the best Christmas and New Year present Kenmare could have as it means so many bed nights and a huge spin-off for the entire community," he said.
Mr Brennan and his wife Gwen bought the manor and its 36 acres from AIB in 2011.