"Our minds are still spinning," one of the family members said.
"I checked it and couldn't believe it that we had all of the numbers. I must have checked it 10 more times."
"I shouted out loudly, 'It's us!"' another family member said.
"I told my children and everyone started crying. We just couldn't believe it."
The family planned to spend the New Year break celebrating their life-changing win and letting the news sink in.
They normally bought tickets a few times a month but had decided to treat themselves to two tickets for both December 23 and 26.
They had visited the supermarket to confirm their win, leaving New World Waitaki buzzing, said owner Greg Flannery.
Waitaki Mayor Gary Kircher said he was pleased the prize went to a family from the district.
Though there was no shortage of suggestions around the town about how to spend the money, he hoped whoever won the big prize would simply enjoy the windfall.
He said there were a lot of great community projects in and out of Oamaru if the family was keen to help out, but understood it was a personal choice.
"Eighteen million can do a lot of good."
People in the streets of Oamaru were overjoyed to hear a local family had won the Lotto jackpot.
One woman said it would help put Oamaru on the map.
Another said she would be worried about everyone finding out who had won the prize in such a small town, but most were pleased the family could now set their children up for life, invest or buy a house.
One woman said it was too mind-boggling to think about what she would do with $18m if she won it.
