He believed Ms Markle and his late mother, Diana, Princess of Wales, would have been "thick as thieves... best friends".
Prince Harry visited the city in May 2015, his first visit to New Zealand, and was an instant hit.
Libby Parsons, 11 at the time, got to high-five a prince and said: "I got lucky enough to just reach out at the right moment and get a high-five".
"I felt so excited I nearly burst. I'm going to tell everyone at school."
Reaction to the prince's marriage plans were mostly positive yesterday.
Whanganui district councillor Josh Chandulal-Mackay, who is on the executive of Monarchy New Zealand, said while the marriage had no constitutional implications for New Zealand, there were benefits for his cause.
"What it does do is generate good publicity again," he said.
"What we saw in 2015 was when Harry came here was he bought the Monarchy back into the public light. In my eyes anything the highlights the relevance of constitutional Monarchy in New Zealand is a good thing."
Mr Chandulal-Mackay said some people enjoyed the celebrity of a royal wedding.
"But predominantly it's about an interest in an institution which carries so much history, and long may it continue."
Whanganui has a strong connection with the royal family with Prince Edward having tutored for six months at Wanganui Collegiate in 1982.
"It's nice to have that long term connection," Mr Chandulal-Mackay said.
