The All Blacks showed their appreciation for his backing of the men in black in a social media post.
“Welcome to the All Black family brother 🖤,” they wrote, prompting a flurry of comments from fans.
“Guess that means we gotta beat the vegemite out of the Wallabies,” one person wrote.
Another planned to show their support at Kahan’s second Auckland show tonight.
“I will be wearing my All Blacks gear at his show tonight and keeping track of the game on my phone!!”
While Kahan takes the stage at Spark Arena tonight, the All Blacks will face the Wallabies at Eden Park, with the match kicking off at 7.10pm.
It is the first of two tests against Australia, with the All Blacks yet to lose a game at Eden Park since 1994.
Kahan was pictured playing a round of golf and enjoying a pint with All Blacks great Justin Marshall earlier this week, with the sportsman sharing a carousel of images from their day together.
“Awesome people, amazing golf course and brilliant day,” Marshall wrote.
“If you are going to Noah’s concerts here in the next couple days you will love it and his music.”
The Vermont-based folk musician is best known for his song Stick Season, which became a global hit in 2022.
His newest album is said to feature Kahan at his “most honest, reflective, and emotionally resonant – grappling with success, identity, family, distance, and the unspoken truths that separate people from one another”.