Huge boulders – which have been used to create a seating area – have been delivered by the company with the help of W M Donald Ltd and placed within the newly developed circular route at the south end of the Moss.
Major improvements have been made to the area by the conservation group in recent years.
As well as campaigning to have the area designated as a Local Nature Reserve, founder member and chair Denise Martin has led the nine-strong group in introducing boardwalks and bridges and worked to clear paths to create a picturesque circular route for walkers.
And in 2007 the PMCG received thousands of pounds via a Scottish Executive grant to maintain and improve the moss.
Denise Martin said: "The boulders are perfect for their required use, which is to be as a seating area."
"The addition of this feature will, we hope, open up the Moss to a wider cross-section of the community and help raise awareness and appreciation of this often overlooked yet very important proposed Local Nature Reserve which is an area of natural diversity."
Neil Thomson, Senior Development Manager for Stewart Milne Homes North, said the company hoped their contribution would be of benefit to Portlethen community.
He said: "We are delighted to have been able to assist the Portlethen Moss Conservation Group with this project. We have worked in partnership with local Civil Engineering Contractors W M Donald Ltd and have been able to supply some materials from our nearby housing development at Leathan Fields Portlethen. We look forward to seeing how these will be used to benefit the Portlethen Community."