Kirkup was born in Perth to Penni Hulston and Rob Kirkup. His mother was an immigrant from New Zealand, while his father was Australian. Zak Kirkup's paternal grandfather was Aboriginal – a member of the Yamatji people of the Mid West. He has one half-sister, who was born when his mother was 17 and given up for adoption.^[3][4]

He grew up in the eastern suburbs around Midland. Kirkup attended Woodlupine Primary School in Forrestfield and Governor Stirling Senior High School in Woodbridge.

Kirkup worked as a research assistant to Matt Birney (the state leader of the opposition at the time). He later worked in the office of Senator Judith Adams, as a campaign officer at the 2007 federal election, as deputy state director of campaigns (under Ben Morton), and in the office of Premier Colin Barnett as an adviser on environmental issues.^[3]

In 2012, Kirkup was named and subsequently cleared in a Public Sector Commission investigation into alleged breaches of the code of ethics that binds WA ministerial staff. The investigation was triggered by an incident at a Perth pub. Kirkup was drinking with a colleague from Barnett's office who falsely informed journalists that then opposition leader Mark McGowan was at the same pub. The colleague also distributed an image of McGowan's home. Kirkup denied any knowledge of his colleague's actions, which the Commission accepted.^[5]

After the 2013 state election he switched to the private sector for a period, finding employment as a consultant with building company BGC.^[6]

In April 2016, Kirkup won Liberal preselection for the state seat of Dawesville, replacing the retiring former deputy Liberal leader Kim Hames.^[7] He won the seat by only 343 votes at the 2017 election, narrowly avoiding becoming a victim of the significant state-wide swing to the Labor Party. Kirkup was one of only thirteen Liberals in the parliament and one of only four in seats outside the metropolitan area.^[8]

In 2020, Kirkup was criticised for his remarks on Clive Palmer's defamation suit against Premier Mark McGowan. State Government lawyers had lodged a counter claim to Palmer's action, a move intended to offset any damages awarded to Palmer. This prompted Kirkup to call McGowan "a princess" who needed to "harden up".^[9]

After Liza Harvey's resignation four months out from the 2021 Western Australian state election, Kirkup said he would run to be leader. While Kalgoorlie Liberal MLA Kyran O'Donnell publicly opposed Kirkup's tilt, citing his narrow margin in his seat of Dawesville,^[10] Kirkup said that he was "up for the fight" in the upcoming election and he stated that all Liberal policies would be under review in the lead-up to the election.^[11] At the resulting leadership election, Kirkup was elected leader of the Liberal Party unopposed.

Premier Mark McGowan criticised Kirkup and the Liberal Party of WA, stating that they remained a "big risk to the state", and that the constant leadership changes meant the party was "blowing itself up and becoming a train wreck". McGowan also took aim at Kirkup's perceived lack of experience, stating the Liberals were "inexperienced, risky and divided... We are three months from a state election and they don't have any policies. They have had four years to get policies ready and they don't have any."^[11]

On 25 February 2021, 16 days prior to the 2021 Western Australian state election, Kirkup admitted he did not expect the Liberal Party to win the election. At the time, polls suggested that Labor could pick up a 12.5 percent swing, which would have cut the Liberals down to as few as two seats. Kirkup said that his main priority was ensuring the Liberals would be able to form a credible opposition, arguing that a Liberal party room reduced to the single digits would be in no position to stop Labor if it went "too far". The move for a leader of a major political party to concede an election before it occurred was unprecedented in Australian politics.^[12]

At the election, amid a massive Labor wave that swept through Western Australia, Kirkup was heavily defeated by Labor challenger Lisa Munday, suffering a swing of over 14 percent.

Since the 2021 election, Kirkup has moved to Subiaco, Western Australia.^[13] In around May 2021, Kirkup co-founded Kolbang Pty. Ltd., an Aboriginal operated electrical contracting business.^[14][15][16]

Kirkup married in February 2018,^[17][18] but separated from his wife in October 2019.^[19]

In December 2020, Kirkup revealed that he had been diagnosed with depression during the previous summer and had subsequently undergone treatment.^[20] Kirkup said that if people are "worried about the fact that that might make me a worse or better leader, I can promise you I understand the emotions that I've experienced, and I've got help and I've got through it."^[20]

Conflict of interests concerns were raised over Kirkup's relationship with Jenna Clarke, the assistant editor of The West Australian Kirkup said that "those issues have been dealt with from a conflict of interest perspective now... between Jenna and her bosses over at Seven West."^[11][8]

• List of Indigenous Australian politicians

• Mr Zak Richard Francis Kirkup - Biographical Register of Members of the Parliament of Western Australia