The former Old Golds No 8 scored a try and finished with a player-of-the-match performance helping Ireland beat Japan 36-20 in Newcastle last weekend.
"I’m so privileged to be able to wear this jersey — what a win," Jansen said after the game.
"Dream come true."
Jansen, whose family and friends made the trip to Australia to see him in action, finished with a try, 48m gained, 12 carries and made all of his 14 tackles.
He grew up in Dunedin, went to Otago Boys’ High School, impressed with Green Island and spent a season on loan to North Otago in 2021.
Jansen, who qualifies for Ireland through his grandparents, played 15 games for Leicester before joining Irish club Connacht.
The block-busting back-rower earned selection for the national team after a standout season for Connacht, scoring 10 tries in the United Rugby Championship and ranking third in tackles made as his team qualified for the Champions Cup.
Ireland play the All Blacks at Eden Park tomorrow night with Jansen a chance to feature.
