Peter Matthew Siddle was born in Traralgon, Victoria. He grew up in Morwell, Gippsland, and began playing cricket at the age of 14 for the Latrobe Cricket Club. As a teenager, he experienced success at under-17 level taking 11/47 in a state match, breaking the Victorian state record set by John Scholes. In 2003, Siddle attended the Australian Cricket Academy and made his first-class debut playing for Victoria against a touring West Indian side at Melbourne in November 2005. In 2006 he attended the Academy again and was offered a full contract with the Victorian Bushrangers for the 2006–07 season. After that, despite suffering a number of shoulder injuries which limited his playing opportunities, he became a regular in the Victorian side.
Siddle lost his position when Clark recovered, only to regain it when the elbow injury recurred prior to the First Test against South Africa at the WACA, 2008. He broke through with three wickets in front of his home crowd at the Melbourne Cricket Ground during the Boxing Day Test against South Africa on his way to figures of four for 81 in the first innings. Siddle backed this performance up in the next Test at the Sydney Cricket Ground, taking five for 59 in South Africa's first innings. His efforts were not enough, however, to prevent Australia from succumbing to a historic home series defeat.
Siddle also gave a fine account of himself on the South African leg of the rubber, in which the Australians triumphed 2–1. Going into the 2009 Ashes series, he had notched up 29 Test wickets at an average of 27.65. That it had come in six Tests against the South Africans and one in India, and with an economy rate of only 2.57 an over, made his record still more impressive. In the first Test of the 2009 Ashes Series, Siddle took 2/97 in the first day's play. In the fourth Test of the 2009 Ashes Series, Siddle took 5/21 in the first day as his career best.
On 25 November 2010, Siddle's 26th birthday, he took a Test hat-trick amongst his six wickets in the first Test of the 2010–11 Ashes series, taking six for just 54 runs, his best ever in test match cricket as he bowled 16 overs in total. On 29 December 2010, Siddle scored 40 in the 2nd innings of the 4th Ashes Test at the MCG, his highest score in first class cricket. Following the end of the 4th Test, Siddle was ranked 9th in the ICC Test Player Rankings.
Siddle took his 100th Test wicket at the SCG on 3 January 2012 in the second Test of Australia's home series against India. During the same series he rose to a career-high seventh in the ICC's Test bowler rankings. He was named the man of the match in the fourth and final Test of the series, having taken 5/49 in the first innings. He took 23 wickets in the series at an average of 18.65.
On 24 March 2013, Peter Siddle became the first number 9 batsman to score a half century in both innings of a Test match.