Miss Clark, the first woman to be elected prime minister, received the insignia formerly worn by Sonja Davies who died in 2005.
The award, announced in the New Years honours list, is limited to 20 living New Zealanders .
At a ceremony at Government House in Auckland Governor General Sir Anand Satyanand said the order, instituted by royal warrant in 1987, was awarded "for outstanding service to the Crown and the people of New Zealand in a civil or military capacity".
Miss Clark was prime minister for nine years from 1999 to 2008.
"Without doubt, Helen Clark's career in the national and international arena easily fits the criteria," said Sir Anand.
He said the description of the prime ministerial role as "primus inter pares" - first among equals - might have applied 100 years ago but it was not a sufficient description today.
The prime minister was now expected to have an encylopaedic knowledge of all domestic and external events "and be ready to expound on any issue raised in any context or forum."
He said the time needed to absorb briefings and master the relentless flow of issues requiring prime ministerial attention was punishing for any individual .
The prime minister's role was inherently lonely, and while many decisions were made by the cabinet, some were made by the prime minister alone and the prime minister had to take responsibility for the decisions.
"For almost nine years Helen Clark shouldered both the powers and responsibilities of being prime minister confidently and adeptly."
He said only four others had held the office for longer and that spoke much of her acumen, abilities and judgement, he said.
"Regardless of anyone's political disposition, I do not believe anyone would question that Helen Clark always strived to do her best for New Zealand and New Zealanders."
