Mr Hayes, 65, won the seat in 2005 with a majority of 2752, increased that to 6758 in 2008 and again to 7135 in 2011.
In December he took up an offer from the Times-Age to share a regular political column in the newspaper with Labour candidate Kieran McAnulty and the Green Party's John Hart.
On Friday afternoon, when the editor called him to remind him about his column, Mr Hayes said he was busy trying to preserve an airline service for Masterton.
Mr Hayes had earned criticism from the constituency for being more involved in parliamentary and overseas roles.
Mr McAnulty dubbed Mr Hayes "the invisible MP" when he was confirmed as Labour's candidate.
Wellingtonian Alastair Scott, who owns Matahiwi Wines in Wairarapa, announced in October he would step forward to contest the National Party nominations for Wairarapa.
Mr Scott said on Saturday he found out about Mr Hayes' decision via a text from a friend.
He confirmed he would be putting his name in the hat at the National Party AGM on February 24 and expected "a couple of names" would also step up.
He warned a candidate might not be chosen at that date.
"The AGM is where it will all start, but it's up to the executive of the National Party in Wairarapa.
"I'm just going with the flow."
Mr McAnulty said he wished Mr Hayes well in his retirement.
He said his departure eliminated the "power" of an incumbent MP.
"Overnight Wairarapa has become a marginal seat again.
"The slate is clean, people have to think about who they vote for."
Mr McAnulty thought it likely that other contenders would enter the contest.
"The flood gates will be open. It's anyone's game."
Mr Hayes is the chairman of Parliament's Foreign Affairs, Defence and Trade Select Committee and has been a New Zealand ambassador in Iran and Pakistan.
He received the New Zealand Order of Merit for contributing to the resolution of the Bougainville conflict.
By completing three terms Mr Hayes qualifies for some retirement privileges, including travel allowances.