MacKellar held a variety of roles in his 20 years at SKM in Australasia, Europe, Africa and the Middle East and led SKM's acquisition of the Enviros Group in the UK in 2009.
MacKellar left SKM in June, following the takeover of the Australian group by Jacobs.
As SLR's international operations director, MacKellar will be responsible for all operations outside of North America, including those in Australia, New Zealand and the UK.
"I have followed SLR's progress over the years and have been excited by its approach," MacKellar said.
“SLR’s international growth has been particularly impressive, as has its disciplined focus on providing purely environmental services, which has contributed to the firm’s ongoing success. I believe SLR has a very strong platform from which to continue to build one of the world’s leading environmental consultancies.”
SLR's Asia Pacific managing director Peter Georgiou commented: “We are excited to be able to draw upon Peter’s wealth of international experience and especially his broader water and environmental consultancy expertise in the Asia Pacific region”.
