[2][3] He is known for his roles as Ricky Baker in Hunt for the Wilderpeople (2016), the highest-grossing New Zealand film in history, as Russell "Firefist" Collins in Deadpool 2 (2018), and as Belsnickel in The Christmas Chronicles 2.

Julian is of Māori descent and is a member of the Ngāti Hauā iwi (tribe), part of the Tainui tribal confederation.

[citation needed] Dennison continued with acting and was given a role in an advertisement for the NZ Transport Agency to discourage driving under the influence of drugs.

The public service announcement, which became an internet sensation in New Zealand and Australia,[8] was directed by Taika Waititi, who later asked Dennison to star in his film Hunt for the Wilderpeople (2016) without the need to audition.

[9][10] In 2020, Dennison co-starred in The Christmas Chronicles 2, portraying Belsnickel and also voicing his elf form, and in 2021, he had a large supporting role in the monster sequel Godzilla vs.