Grant Elliott will play for Birmingham Bears in this summer's NatWest T20 Blast.
The all-rounder has signed a 'Kolpak' deal which draws a line under an international career with New Zealand stretching back nine years.
Elliott, 38, top-scored for the Kiwis in the semi-final and final of the 2015 World Cup and last appeared for his country in the World Twenty20 last summer.
Warwickshire's sport director Ashley Giles said: "Grant has proven himself as a match-winner on the biggest stage.
"Securing Grant, and the earlier addition of [fellow New Zealand all-rounder] Colin de Grandhomme, gives us the additional batting firepower that we wanted to complement a strong top order.
"He also gives us even more options with the ball and has good experience of English conditions."
Elliott said: "I'm very excited. Edgbaston is a fantastic place to play cricket, and I'm really looking forward to taking to the field as a proud Bear and hope to contribute to more success for the club in 2017."