Families and youngsters gathered inside the foyer at Melbourne's Royal Children's Hospital and on above sky bridges on Tuesday morning ahead of the couple's arrival.
Prince Harry and Meghan Markle shook hands with dozens of well-wishers and took time to speak with gathered crowds, offering hugs and waves to others.
Workers also clamoured at the windows of their offices above watching on as the couple walked past.
When asked by a journalist what he was most looking forward to about being Down Under, the prince replied "everything".
"It's good to be back," he said.
The hospital was previously visited by Queen Elizabeth II and in 1985 by Princess Diana and the then-prince Charles.
Their second engagement on Tuesday will take place at a centre delivering homeless services for women and was chosen to reflect Meghan's commitment to community-led support for vulnerable women.
But other planned appearances are decidedly more commercial - and controversial.
Organisers of a three-day women's retreat say Meghan will headline the exclusive event - pitched as a "girls weekend like no other" - while Harry is set to deliver a keynote speech on workplace mental health at a Melbourne summit.
Tickets to the retreat start at $2699, while in-person attendance at the summit will set punters back about $1000 or more.
The privately funded trip is not an official royal tour, with the couple no longer working members of the royal family after renouncing their status and moving to the US in 2020.
But for Giselle Bastin, a Flinders University associate professor and expert on the British royal family, the decision to use their titles to pursue private interests will be perceived by many as a conflict of interest.
"It's well known that the Sussexes are in dire need of income and so a staging of a quasi-royal tour to Australia is being regarded as a rather desperate attempt to monetise their status as royalty," she told AAP.
"During the 2018 tour, Meghan was overheard to say that she couldn't believe she 'wasn't being paid for this', and the irony is that this time she is coming to Australia and being paid."
During their headline-grabbing trip almost a decade earlier, adoring crowds clamoured to catch a glimpse of the newlyweds and much of the nation gushed as news of Meghan's pregnancy was announced.
"By contrast in 2026, the Sussexes have ceased to be working royals and have used media platforms to air their grievances about the royal family," Assoc Prof Bastin said.
"They are thought to have cast a shadow over the final years of the late Queen Elizabeth II and the Duke of Edinburgh, and for this they have attracted the ire of many a royal follower."
Adding to the shift in public sentiment has been police confirmation taxpayers will cover additional security costs and public safety operations, contradicting repeated assurances from the couple's team that the visit would be entirely privately funded.
An online petition calling for Australian taxpayers not to foot the bill has attracted more than 45,000 signatures.
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