Armstrong, 23, signed a multi-year extension with the team that has been the long-time home for six-time series champion and compatriot Scott Dixon.
After three years of competing in the Formula Two Championship, Armstrong made his IndyCar debut this year on a contract in which he competed exclusively in road and street course races.
The former Medbury School student has racked up enough points in his 11 rounds of action - including three top-eight finishes - to sit 20th on the overall standings and lead the rookie driver standings with one race remaining.
Armstrong's new contract will expand to include oval racing next year, a prospect that excites him.
"Together with this very talented and experienced team, I am confident we can compete at the highest level in this championship," he said.
"I feel very grateful that Chip has given me the time to adapt to Indycar and has helped me every step of the way in what has been a good season.
"With a season under my belt, I now want to turn these lessons into results. I will be racing on the ovals for the first time next year and it's an exciting challenge that I'm confident I can learn quickly.
"I spent the entire month of May either in the engineering office or in the pit stand this year, trying to familiarize myself with the details of oval racing. It's a challenge that excites me a lot."
Three New Zealanders are set to contest next year's championship, led by Dixon - who is poised to finish second this season - Armstrong and Team Penske driver Scott McLaughlin.
