Sadler passed away peacefully in a Wellington hospital aged 92.
NZRU chairman Jock Hobbs said: "It is significant to lose one of the few living links with our rugby heritage from that era.
"Like all other All Blacks, Joey Sadler had his own unique story about his rugby career, which was cut short by injury, and his life beyond rugby. However, his loss will be most keenly felt by his family and friends and I would like to extend my sympathies to them."
Sadler was, at the time of his passing, the second oldest surviving All Black.
The eldest, Eric Tindill, is also the eldest New Zealand Test cricketer, having also played for the Black Caps before World War II.