Santner has previously captained in 24 T20Is and four ODIs and his first series in the full-time role will come against Sri Lanka from late December.
The first major event in his tenure will be February’s Champions Trophy before focus turns to building to the 2026 T20 World Cup.
“It’s obviously a huge honour and a privilege to be asked,” Santner said. “When you’re a young kid the dream was always to play for New Zealand but to have the opportunity to officially lead my country in two formats is special.
“It’s a new challenge and I’m excited to get stuck into the important period of white ball cricket that we have ahead of us.”
Head coach Gary Stead explained that they were conscious of not adding to Tom Latham’s workload as Test captain. Santner is also a first-choice selection across both white-ball formats.
“In Tom Latham we have an accomplished and experienced captain who has led the side admirably across all three formats,” Stead said. “Tom’s doing a great job as full-time Test captain since taking over in October and we’re keen to allow him to focus on that job which requires a considerable amount of time and energy.”
“Mitch is a fantastic team man and leads by example in all facets of the game. He’s an incredibly calm and collected personality and he has a huge amount of respect in the changing room, which will serve him well.
“He’s had plenty of experience leading the T20 side and did a good job when he captained the ODI team last month, so he already has a good understanding of what it means to lead the team. I’m sure Mitch will also bring his own ideas and style of leadership to the role.”
Santner has recently enjoyed a resurgence of his Test career with Player of the Match performances against India in Pune and England in Hamilton but New Zealand now have a light schedule in the format during 2025.