Prior to entering parliament Duniam was a political staffer, including as deputy chief of staff to Tasmanian premier Will Hodgman.

[5] Duniam grew up in Somerset, Tasmania, attending Stella Maris Catholic Primary School and Marist Regional College in Burnie.

[1] In April 2016, Duniam was preselected in third position on the Liberal Party's Senate ticket for the 2016 federal election, ahead of incumbents David Bushby and Richard Colbeck.

In April 2021, while being interviewed by Rita Panahi on Sky News, Duniam claimed that Greens senator, Sarah Hanson-Young, had exposed her young niece to danger by involving her in an environmental protest at a logging work site.

Duniam has been critical of the Albanese Government's decision to provide $8.2 million in taxpayer funding to the controversial "Environmental Defender's Office" (EDO).

[12] Which was placed under consultation on 30 November 2023 by Environment Minister Tanya Plibersek,[13] a decision that Duniam has fought with the local community in Strahan against.

[21] In 2023, Duniam campaigned against the Albanese Government's failed indigenous voice to Parliament and predicted that the majority of Tasmanian's would vote No.

[22] As of 2017[update] Duniam had three children with his wife Anisa, whom he met at university, and lived on a "small acreage outside of Hobart".