AgResearch Invermay Agricultural Research Station will celebrate the anniversary today, bringing current and former staff back to the Mosgiel-based facility.
Organising committee member John McEwan said it was a significant milestone because "it’s 75 years".
Invermay was established in July 1949, and in 1992 the facility was transferred to AgResearch Ltd.
The last reunion was held to mark 50 years, which Mr McEwan attended.
"It’s an opportunity to get everybody back together because 25 years is a long time ago and there's a few people who won't be around for very much longer."
Between 120 and 130 people are expected to attend, including past and present employees.
AgResearch has about 60 staff based at its Invermay facility.
Many were involved in sheep, deer, climate change, freshwater and genomic research.
"A lot of people won’t have seen each other for quite a few years ... there’s definitely a bit of buzz going on that front."
Attendees will be given a tour of the campus to showcase the current research and the research done over the past 25 years and the impact it has had on the agricultural industry.