"It warms the cockles of my heart," Prof Fleming said this week about the honour.
She is professor of science communication at the university's Centre for Science Communication, and the companion title was bestowed on her at a function in Dunedin on Tuesday night.
The title also recognises "contributions to the promotion and advancement of science and technology in New Zealand".
Prof Fleming's father, the late Sir Charles Fleming, former chief palaeontologist at the New Zealand Geological Survey, was a former president of the New Zealand society.
Prof Fleming believed the award largely acknowledged her work with the university centre over the past three years.
The president of the New Zealand society, Dr Garth Carnaby, said Prof Fleming had a "wonderful reputation" for her work as a science communicator and her commitment to taking science to the community was well known in New Zealand and overseas.
"She has also devoted an enormous amount of energy to popularising science, at the same time as pursing a biology research career," he said.
She was a founding member of the New Zealand International Science Festival, held every two years in Dunedin, and is an executive member of the festival.
Dame Elizabeth Hanan, who has been the driving force behind the festival, is also a companion of the society.
Prof Fleming has also been involved for many years in Hands-on Science, a successful science summer camp for high school students from around New Zealand, held at Otago University.
In 2000, Prof Fleming was a commissioner on the Royal Commission on Genetic Modification, which travelled throughout New Zealand holding public meetings.
