Hundreds of people gathered on Wednesday in the city's main square, framed by medieval and Renaissance buildings, and in nearby streets to greet Kate.
Some waved Union Jacks while others held a banner reading "Ciao Kate".
Kate, the wife of heir-to-the-throne Prince William, was starting a two-day visit as part of her work focusing on childhood development, a central theme of her public work.
"Undoubtedly, this is a huge moment for the princess. There will be many highlights of 2026, but this being her first official international visit post her recovery, this is a really significant moment for her," said an aide to the princess.
Wearing a light blue trouser suit, the princess greeted children waiting for her outside the Town Hall.
"Buongiorno, what's your name?" she asked a preschool girl in Italian, a city official said, recounting the exchange.
"My name is Camilla, and yours?" the child replied.
"I'm Catherine," the princess said — prompting a brief look of surprise before Camilla, who expected to hear the name Kate, exclaimed: "But she's called Catherine."
The visit will centre on the "Reggio Emilia approach", which places relationships, the environment and community at the heart of a child's development.
In her meetings with administrators, teachers, parents and children, Kate will focus on the historical roots of the city's schools, the role played by women, the connection between nature and learning, and the involvement of the local community, officials said.
After World War Two, residents of Reggio Emilia - many of them women - helped finance some of Italy's first nursery schools by selling scrap metal from military equipment abandoned by retreating German forces.
Pioneering schools for children under six took shape there decades before national legislation governing preschools was adopted in 1968.
Kate is expected to visit two public pre-schools, where classrooms are organised around open communal spaces known as piazzas, with in-house kitchens and studios that encourage children to experiment with materials, colours and sounds.
The Princess of Wales will be joined by key figures who helped develop the Reggio Emilia approach, such as Ione Bartoli, 95, a former regional councillor in the 1970s.
"The princess's visit is an honour and recognises what we in Reggio Emilia have achieved together for our children," Bartoli told Reuters.
