Coach Scott Robertson first appointed Ellison to an assistant coach role with the All Blacks in 2023, and after Leon MacDonald departed the side in August, Ellison was given extra responsibilities.
Ellison said he was excited to step into a full-time role with the All Blacks.
"As a player, it's the pinnacle of your playing career to wear the black jersey, and it's no different as a coach."
Ellison played four Tests for the All Blacks, debuting against Italy in 2009 and playing Ireland, South Africa and Scotland in 2012. He also played against the Barbarians for New Zealand in 2009.
A product of Porirua's Mana College, between 2003 and 2016, Ellison played for Wellington (45 games), Otago (6), Blues (1), Hurricanes (53), Highlanders (23) and the Rebels (36). He also played 57 games for Ricoh Black Rams in Japan. He also won a gold medal at the Commonwealth Games in Sevens in 2006.
New Zealand Rugby's general manager of professional rugby and performance, Chris Lendrum, said it was 'great to see Tamati's progression through the New Zealand Rugby coaching pathway as he's developed his craft with the Wellington Lions in the Bunnings Warehouse NPC, then with the Crusader in DHL Super Rugby Pacific.'
As a result of his appointment, Ellison ended his connection with the Crusaders.
Crusaders chief executive Colin Mansbridge said the organisation was proud of his appointment.
"He's had a huge impact over the last couple of years with us and we thoroughly appreciate his contribution."
Crusaders coach Rob Penney said he was unsurprised in his elevation to an All Blacks role.
"To have someone who can coach both sides of the ball at an elite level is rare."
Penney said discussions are underway with potential replacements, and the Crusaders were excited about the possibilities ahead.