Woodville's Brown, 34, has also joined the board.
Rebecca chairs the contest committee which oversees the running of the prestigious FMG Young Farmer of the Year.
She was elected to the position on Sunday and is the first woman to hold the role.
"I'm really honoured. It's a cool feeling and shows women can do anything," said the mother of five.
"I love being on this side of the contest. My husband Angus Brown was a grand finalist in 2010. I've been around the contest for 15 years and we even convened a couple of regional finals as well," she said.
The changes mean half of NZ Young Farmers' eight-member board are now women. The fourth is appointed Dunedin-based director Sharon Angus.
"It shows we're leading the way in ensuring our board reflects our evolving membership base," said NZ Young Farmers Board chairman Jason Te Brake.