Dressed in vibrant purple, the one-time Sydneysider turned Danish royal charmed schoolchildren and fans with hugs and handshakes outside the $80 million Lowy Packer Building in Darlinghurst.
The building is the new home of the institute named after Victor Chang, the distinguished heart surgeon who was gunned down in 1991 after a failed extortion bid.
As well as the Victor Chang Cardiac Research Institute, the facility will house scientists from nearby St Vincent's Hospital, where Dr Chang worked until his death.
Princess Mary, an honorary life governor of the institute since 2005, said she had been following its "groundbreaking and world-class" work.
"(This building is) a new home that will provide a state-of-the-art research environment for some of the brightest and best minds in the country and the world," she said.
Princess Mary said heart disease remained a leading cause of death and disability in the community, and made a reference to her mother Henrietta's death from the disease in 1997.
"Given my personal experience with the devastating effects of heart disease, and as patron of the Danish Heart Association, it was with great interest that I visited the Victor Chang Institute in March 2005," she said.
"It gave me the opportunity to learn about the research being conducted at the institute and while I cannot profess to have understood all the detail of the work, I can say it was quite clear that the institute's works were not only fascinating but clearly groundbreaking and first class."
The facility was funded jointly by the state and federal governments, with contributions from the families of property tycoon Frank Lowy and the late media magnate Kerry Packer.
Members of both families were present at the opening on Wednesday - including James and Erica Packer, who recently celebrated the birth of their first child.
In his address, Premier Morris Iemma welcomed Princess Mary to Sydney, "a place where you command such affection and respect".
"Facilities like these are where the future of Australia is being determined, where the high-skilled, high-tech jobs are being created, where our reputation for innovation is deepened every single day and where our quality of life is being rewritten," he said.
Cardinal George Pell blessed the building after Ann Chang joined the guest of honour in unveiling a life-sized bronze sculpture of her late husband, dressed in surgical scrubs, in the forecourt of the building.
"(This is) a statue that will forever honour (his) vision, memory and caring," Princess Mary told the assembled dignitaries.
"A statue that celebrates his achievements and serves as inspiration to others who believe in his dream of a world free of suffering from heart and other diseases."
Princess Mary also praised Dr Chang as "an original thinker ... known for his legendary caring for his patients and their families".
