This began a rapid ascent for the young second five-eighth who was in line to be part of the Waikato squad for the 2013 ITM Cup until a shoulder injury ruled him out.

During the 2022 Super Rugby Pacific season Lienert Brown played four games for the Chiefs before acquiring a shoulder injury.

[10] Lienert-Brown was called into the All Blacks' Rugby Championship squad for the injured Sonny Bill Williams, making his debut in the starting line up against Australia in Wellington on 27 August 2016, following concussion to Ryan Crotty.

Lienert-Brown started another five times in 2016, scoring the second try of his international career in the third Bledisloe Cup test against Australia before being replaced by Fekitoa in the 62nd minute of the All Blacks' 37–10 win over the Wallabies.

Lienert-Brown was selected in the All Blacks' 33-man squad for the 2017 Pasifika Challenge against Samoa and three-test series against the touring British and Irish Lions.

However, the team stepped up significantly for the second Bledisloe Cup test in 2019, with Lienert-Brown winning Man of the Match in the 36-0 thrashing at Eden Park.

On 28 August, All Blacks Head Coach, Steve Hansen named Lienert-Brown as one of 31 players in New Zealand's squad for the 2019 Rugby World Cup.

[17] In 2021, Lienert-Brown started an RTD beverage brand named "Grins", with his former Chiefs teammates, Damian McKenzie and Stephen Donald.