It started innocently enough, as the pair - who had not seen each other for about 50 years - left a cocktail party held at the school grounds on Friday night for a smoke outside.
School principal Whetu Cormick said the pair - whose names were not available - were among a group of former pupils outside, and quickly struck up a conversation.
However, things took a romantic turn when the man confessed to a schoolyard crush on the woman, dating back to their classroom days, Mr Cormick said.
Things got slightly more interesting when the woman confessed to having been separated for the past three years, he said.
"They hugged one another and arranged to meet up for coffee later," he said.
"Everyone just stopped talking and then they all started clapping."
Nearly 400 former pupils from around New Zealand and Australia were in Dunedin at the weekend for the school's combined reunion.
The event marked the history of both Macandrew Rd school, 1883-1939, and Macandrew Intermediate, 1940 to the present.
Among those attending were 65-year-old twins Loraine Morris and Valerie Hobbs, of Christchurch.
Mrs Hobbs had spent 33 years living in Australia before returning to Christchurch this year, and was enjoying renewing bonds with her twin and another sister, Irene Currie (63). of Dunedin.
"That was another nice reason to come back, because my twin's here and my sister is here.
"To be back together is actually quite lovely," Mrs Hobbs said.
And it was also a big day for members of Dunedin's Chinese community, with members of several extended families to attend the school at the reunion.
Among them, Phillip Shaun (61) said he was one of eight siblings to be taught at the school, and many in the Chinese community went to the school and still knew each other.
Some people at the reunion he was seeing for the first time in 40 years - but old ties were quickly renewed.
"Being Chinese, they know the families, they recognise the name and they say `do you know so-and-so'," he said.
"With eight in the family, someone has gone to school with someone here," he laughed.
