After gaining his initial degree, he worked as a practising veterinarian for a time, both in Australia and overseas, and later became involved in marketing and management roles in the animal health industry.
[12] Leyonhjelm lives with his wife, Amanda, in Sydney, but also owns a rural property in Hargraves, a locality near Mudgee in the Central West region of NSW.
[21][22] Drawing 0.10 percent of the first-preference vote, Leyonhjelm unsuccessfully contested the Division of Bennelong in 2007 for the LDP,[23] which ran as the Liberty and Democracy Party, after the Australian Electoral Commission initially refused to register it under its original name due to the use of the word "Liberal".
[28] The result for the LDP in New South Wales was partly attributed to the "donkey vote", because the party occupied the first position on a ballot paper with a record number of candidates.
[31][32] In the first sitting week, he successfully moved to have the government's Clean Energy (Income Tax Rates and Other Amendments) Bill considered by itself, instead of being grouped with other legislation.
[37] In August 2015 Leyonhjelm negotiated a deal to include a 12-month sunset clause on the temporary ban on importing the Adler lever action shotgun.
Leyonhjelm has been a vocal opponent of laws designed to reduce the consumption of cigarettes, and has accepted $55,000 in donations from tobacco company Philip Morris.
[43] Day has since resigned from the Senate, but Leyonhjelm has stated he intends to form a new voting bloc with his successor from Family First, as well as Cory Bernardi from the Australian Conservatives.
[50] He subsequently told women's rights activist Melinda Tankard Reist to "STFU" (for "shut the fuck up") when she accused him of hypocrisy.
[51] Speaking to BBC News in November 2016, Leyonhjelm questioned the motives and integrity of anti-poverty charity workers, particularly with regard to a conflict of interest in the continuation of their own employment as opposed to their elimination of poverty and thus their obsolescence: "The people who work for those charities have their careers tied up in the continuation of that charitable work.
He told ABC News: "Taking the pension shouldn't be something you aspire to, it should be something you try to avoid because it signifies you're in a low income group – in other words you're poor or you know, close to poor,"[53] He also opposed the censorship of video games and criticised the Australian Classification Board claiming, "How is it that adults are not trusted to make choices about video games, and yet they are allowed to vote?
[62] When challenged, Leyonhjelm pointed to an interview in which he claimed Hanson-Young accused all men of being rapists, although this was rejected by the senator.
[64][65] On 7 January 2019, Leyonhjelm announced that he intended to quit federal politics to contest the 2019 New South Wales state election on 23 March 2019.
[4][67] In November, Senator Hanson-Young was awarded $120,000 in damages after winning a defamation case in the Federal Court against Leyonhjelm over interviews he gave following his "stop shagging men" comment in Parliament.
[68] Leyonhjelm was due to pay Senator Hanson-Young's legal costs and the associated settlement by the end of 2019 but chose not to do so as he was appealing against the defamation decision, partly on the ground of the implied constitutional freedom of political communication.
[73] In interviews, he has stated that he was initially drawn towards socialism, but turned away from it after travelling to socialist countries in Africa and Eastern Europe and was later influenced by the writings of economist Milton Friedman.
[74][75][76] In the 44th parliament, along with seventeen other crossbenchers (including 10 Greens, independents and representatives from four other parties), the Liberal Democrats shared the balance of power in the Senate.
Upon being described as an "angry white male" for seeking to amend Section 18C, Leyonhjelm lodged a complaint with the Human Rights Commission, arguing that this is a breach of 18C.