The council also agreed to bring money forward to complete the second stage - another four to six sirens between Ōmanu and Mount Maunganui Primary School - at the same time.
The budget for the second stage was yet to be finalised. It would be taken from the budget for more "vertical evacuation structures" such as the one the council built in Gordon Spratt Reserve.
The council was reviewing plans for more such structures based on updated science.
A third phase of installations - sirens in the rest of Mount Maunganui as well as Matua and Welcome Bay - will take longer due to technological challenges.
Morris said the council could have waited until the challenges were resolved and all the sirens could be installed at once, but had opted to do what it could now.
Waiting would have meant it could have been a full two decades on from the 2004 Boxing Day tsunami before the sirens were done, he said.
The devastating event ignited the siren debate in Tauranga, but the project has had multiple false starts since.
He said all of the phase one sirens would be installed on council reserve land "so they're not right next to someone's lounge window".
Locations for phase two sirens were still being identified.
The news was music to the ears of Pāpāmoa mum of one - with another on the way - Renee Ball.
In 2016 Ball, who owns a business in Mount Maunganui, started a petition to get sirens installed along the coast.
Three years on, she said the issue was still widely talked about and newcomers were regularly surprised to hear that Tauranga had no tsunami sirens.
"It's going to put a lot of people's minds at ease."
Once the council "did its bit" with the sirens, it was up to residents to ensure they had a plan in place, she said.
Pāpāmoa retiree Dorothy Seymore was also pleased to hear the long-awaited news.
Seymore said that, like many of her generation, she was not a big mobile phone user and could not rely on her phone to receive Civil Defence alerts.
"I think a siren would be a good idea."
Pāpāmoa Beach Resort owner Bruce Crosby said he had no problem with sirens.
He did, however, wonder about the amount of money being spent on tsunami preparation given the rarity of the events.
It also seemed strange for the council to, at the same time, be preparing to develop coastal land at Te Tumu that would see tens of thousands more people living in the inundation zone.
