Watling represented the Black Caps in 75 Tests, 28 ODIs and five T20Is before retiring in 2021 following New Zealand's victory in the World Test Championship final against India.
He has coached New Zealand domestic teams Wellington Firebirds and Northern Districts, winning the 2025-26 Super Smash and 2024-25 Plunket Shield titles with the later.
"I'm incredibly excited," Watling said. "To come back into the team and work with this current group is a special opportunity and one I don't take lightly.
"What this side and the support staff have achieved together over recent years has been remarkable, so I'm looking forward to contributing to a world-class side."
New Zealand Test captain Tom Latham added: "BJ is a guy who personified what it means to be a Black Cap, so having someone like him come back into the group will be great for our environment.
"There was never any doubt about his effort and determination every time he stepped onto the field, and I'm sure that same attitude will translate in his coaching style."
New Zealand spin-allrounder Michael Bracewell has opted to take up a casual national contract ahead of the 2026-2027 season to pursue an opportunity to play in the Australian Big Bash League.
New Zealand have suffered a blow ahead of next month's home T20I series against India after spin-allrounder Rachin Ravindra was ruled out with a shoulder injury he picked up during a promotional shoot.
New Zealand allrounder Rachin Ravindra could be a doubt for next month's home T20I series against India after dislocating his right shoulder while doing a promotional shoot earlier this week.
New Zealand white-ball captain Mitchell Santner has declined a lucrative offer from Australian Big Bash League side Adeliade Strikers to remain in contention for Test selection.
