The £1 million expansion was granted by councillors in 2012 and the first stage was completed in 2014.
However, phase two has seen a number of issues to overcome including establishing who owned the land and a water mains survey that indicated the mains went across the area of the development.
The phase two upgrade will consist of an expansion to the bus turning area and creating three bus stops.
Each stop will have an enclosed shelter that will be lit and have a real time display through electronic departure boards.
An additional 91 parking spaces are being provided in the upper carpark, including improvements to internal footways and access and an enhanced CCTV system.
Councillor Gillian Owen said: “I have watched these improvements for many years, from the Planning Application in 2012 to today when I visited the Park & Ride to see the improvements first-hand.
"They really are brilliant. Well worth the wait and the pain and anguish of issues with land ownership, a water main running through the site and of course Covid-19.
“The new stances and turning circle are now in operation.
"Just to let you know Stance 1 will serve Aberdeen South, Stance 2 will serve Peterhead/Fraserburgh North, and Stance 3 will serve local services.
"There is still some tidying up to do on site, but passengers will be able to check on the digital timetables when the next bus is due.
"These will be updated throughout the day to give real time updates.”
Gillian concluded: “What a fantastic new facility for Ellon. Can I thank everyone who has played a part in achieving this project?
"And more importantly thank the residents of Ellon who have waited a long time, your patience has been much appreciated.
"I look forward to seeing it completed in the coming weeks.”
It’s anticipated that the project will be completed by February 2022.