Poi, who has 10 test caps for the Silver Ferns, will bring speed and dynamism to the Steel midcourt as they attempt to turn around some disappointing results in recent seasons, including last place in the ANZ premiership this year, with only two wins.
Poi has been with the Tactix for the past seven years, captaining the team in recent seasons.
Her CV includes the Silver Ferns, New Zealand A, the Fast5 Ferns, who won the World Series, and the 2017 World Youth Cup champion NZ-U21 team.
She was named earlier this month as a Silver Ferns triallist ahead of New Zealand's series against England and Australia.
Poi said switching franchises was a tough decision.
"I'm feeling a mixture of emotions to be honest and I feel like it won't really sink in until I fully move down south. I'm a bit nervous but also excited about the new opportunity and getting out of my comfort zone a little," she said.
"With next year being a unique season, I thought, why not? Go challenge myself, get out of comfort zone, refresh and experience a different environment with different players and coaching staff. Change is good sometimes which excites me. But I will miss the Tactix and will always be grateful for the opportunities they have given me to grow as a person and athlete."
Poi said she was keen to add new energy to the Steel environment and help influence a change in the team's fortunes.
"I think if we build a good foundation and connections both on and off the court in preseason, along with some quality trainings that put us under pressure, that will be a good start. Also, making sure we keep the balance and have a bit of fun too."
New Steel head coach Wendy Frew said Poi's move was exciting for the Steel.
"Kimiora ignites play and creates opportunities. When you have someone of her calibre in the mix, everyone is fuelled by that energy and it will be fantastic to add her skills to our roster," she said.
"She has a lot of attacking flair and backs that up with some strong defence for crucial intercepts. Her work rate is exceptional on the court and I'm excited to have her as part of the Steel."
