"This is a huge signing for the Steelers. Dalton is going to bring so much to the squad," Lavea said.
"He's a natural leader and will come into our set-up with plenty of experience to contribute.
"It's no secret last year was a tough one for Steelers fans but we hope this signing will show them our intent ahead of the 2020 season."
For Papalii, the decision to link with Lavea was a no-brainer.
"I'm really excited about joining a provincial union with such a proud history and such wonderful, loyal fans," he said.
"I've got heaps of friends and family out this way and my dad played club rugby in the region so I feel very connected to the place.
"Tai and I also go way back and I know he's going to do great things with the Steelers.
"I can't wait to be a part of that," said the new recruit.
Counties Manukau general manager Aaron Lawton said the Lavea's first Mitre 10 Cup squad was taking shape nicely.
"This is a momentous day for our provincial union, for our fans and our community," Lawton said.
Papalii also confirmed he would be aligned with the Patumahoe club, following in the footsteps of his father, Mark, who played two seasons there.