About 700 staff at two sites in Auckland walked off the job, demanding a wage increase of 5 per cent, in line with the rising cost of living.
The company warned of product shortages because of the action.
First Union said on top of the 5 per cent raise next year, workers will get a nearly 4 per cent boost for nine months in 2023.
Union spokesperson Jared Abbott said the deal included extra sick leave and redundancy provisions, but getting more money in the pay packet was a bottom line for staff.
"The workers said 'don't come back with an offer of less than 5 per cent', and to be able to stand in front of them last night and be able to tell them they were getting their 5 per cent was a really good feeling.
"The vibe and the parties that happened afterwards were a once-in-a-lifetime experience for me."
The agreement also covered hundreds of workers in Christchurch and Palmerston North, Abbott said.
He said the public support for the strikers from gave them a huge confidence boost.
"A huge thank you to the public support, it made a huge difference to these people.
"On the picket line we were having all sorts of people bringing down donations, bringing down food.
"That really really gave people the hope to see this through."
Abbott said the new agreement made them some of the highest-paid distribution workers in the country, and the extra money would make a make a massive difference to their families.
A Countdown supermarket spokesperson said it is very pleased to have reached an agreement with striking workers.
They said staff worked incredibly hard to minimise the impact on customers, but that it will take a few days to properly restock shelves.
