A series of upgrades, refurbishments and the introduction of new facilities will take place at the 1,000-acre Dalkeith Country Park, initially over a two-year period and creating about 35 jobs.
It is pledged the first phase of the redevelopment at the Midlothian park, which is owned by Richard Scott, the 10th Duke of Buccleuch, will be in keeping with the landscape. Plans have gone out to tender, with a main contractor expected to be officially appointed by early September.
The initial works involve the full refurbishment and development of the historic stableyard, the surrounding listed orangery and amphitheatre and a new adventure playground.
The buildings will feature an improved cafe and restaurant, farm shop and bakery, other shops, and an array of supporting retail, with the preferred operating partner close to being announced.
The wider park will have a variety of activities and attractions which, it is said, will provide "exciting, engaging and educational recreation space for families".
Historic Scotland and Midlothian Council are "actively engaged" with the project and are being closely consulted about restoration activities in the iconic orangery, bridges, landscaping and listed buildings.
Ian Herbert, visitor services manager for the park, said: "We are thrilled our plans to revamp the park have been given the seal of approval.
"As well as creating jobs this significant investment will play an important part in facilitating economic development and growth in the region.
"Since the planning application was submitted in February we have been canvassing views via an online survey and are continuing to liaise with organisations such as Scottish Natural Heritage and Historic Scotland. Our next step will be an open day next month where we will be able to give more details of our plans."
It is claimed the park, which is about five miles from Edinburgh city centre, will be modernised in a way that is sympathetic to the style, history and heritage of the current buildings.
One of the more popular activities are the Tough Mudder assault course and race.
Jim Bryant, cabinet member for planning and development at Midlothian Council, said: "Dalkeith Country Park is a great asset to our community.
"It is also the venue for many large scale events, such as Tough Mudder, which brings a wealth of visitors to our area.
"This year, we are looking forward to a bumper year at our second Midfest Festival, with some events taking place in the park.
"We are delighted to be working in partnership with both the park and Historic Scotland to bring these redevelopment plans to fruition."
The open day to view more details of the plans will be on Saturday August 30 at the park's stableyard from noon.
In 2006 the park was in the headlines when protesters took to trees there in opposition of the bypass of the A68 through the area.