The couple have farmed the 186ha property, Glenelg, at Patoka in the Hastings district since 2001.
The structure has since evolved to become a 50:50 equity partnership with Opiki dairy farmers Stuart and Ann McPhail, trading as Great Glen Farming Ltd.
"When you put work into a farm, it's part of your life. It's not just a job or a business. It's home," Nick said.
"We could live anywhere in the world, but this is our spot."
The win was announced at the East Coast awards dinner in Napier on Wednesday night.
It is the second year in a row a dairy farmer has taken out the East Coast's supreme award.
The farm regularly hosts visitors and school groups, including Fonterra Open Gate in 2017.
One of the finals judges, 2018 Horizons supreme winner Helen Long, said the Dawsons showed a strong desire to close the rural-urban divide.
"Nick and Nicky display a genuine passion and enthusiasm for their environment, industry and community; they are generous people, sharing their time and beautiful farm to the public."
"Nick and Nicky exhibit a good sense of pride and respect for people, livestock and the environment," fellow finals judge Alastair Ormond said.
As well as the Supreme Award, the Dawsons won the Bayleys People in Primary Sector Award, DairyNZ Sustainability and Stewardship Award, WaterForce Integrated Management Award and the Predator Free Farm Award.
Run by the New Zealand Farm Environment Trust, the awards champion sustainable farming and growing through a programme where one regional supreme winner is selected from each of the eleven regions involved.
These eleven winners will be profiled at the Awards' National Sustainability Showcase in Hamilton on June 6, with each in the running for the Gordon Stephenson Trophy.