The news is a boost for the Blues who have lost first five Bryn Gatland to the Highlanders from next Super Rugby season.
Tuungafasi joins utility back Damian McKenzie, halfback TJ Perenara, flanker Sam Cane and hooker Codie Taylor as All Blacks who will stick around at least two years beyond next year's World Cup in Japan.
Tuungafasi, who has played 14 times for the All Blacks and 63 times for the Blues, has also re-signed with his Auckland Mitre 10 Cup province.