Hazlewood was raised in the small country town of Bendemeer, New South Wales, situated 40 km north of Tamworth. He is the younger son of Trevor and Anne Hazlewood, having an older brother, Aaron, and sister, Casey. He would frequently engage with his older brother in fierce backyard cricket matches, and by the age of 12 was already playing for Tamworth against grown men. Hazlewood was selected for New South Wales at the age of 17, making him the youngest paceman to represent the state. His first-class debut was at the Sydney Cricket Ground against the touring New Zealand side in November 2008. Hazlewood also became the youngest to make his One Day International debut for Australia on 22 June 2010.

A right arm fast bowler, he has also played for Australia Under-19s and was the youngest member of Australia's squad for the 2008 Under-19 World Cup.

Hazlewood is oft quoted as saying that his efforts bowling during the UAE under 17’s tour side in the Commonwealth Youth Nations Cup in 2007 were what solidified his belief in representing his country at a professional level. He cited bowling at opening batsman Sachin ‘The Dubai Destroyer’ Thampan as his hardest test.

They later dated for almost 6 months, which proved an even tougher test for Josh.

He bowled 7 overs on his One Day International debut and picked up one wicket for 41 runs. He made his T20I debut vs West Indies on 13 February 2013 and picked up 1–36 in 4 overs. He picked career best figures 4–30 in a T20 vs England.

He made his Test match debut for Australia against India at the Brisbane Cricket Ground on 17 December 2014. He took 5 wickets in the first innings, conceding 68 runs. He was a part of the Australian squad for the 2015 ICC Cricket World Cup and played a part in their triumph, picking up 4 wickets against Pakistan in the quarter-finals.

In November 2015, Hazlewood became the first player to achieve the player of the match award in a day-night Test match ever. In this match against New Zealand, he took the first ever wicket in day-night Test by lbw Martin Guptill. He also took the first five-wicket haul in a day-night Test cricket history with the figures of 6 for 70, en route to reaching 50 career wickets in just his 12th Test, faster than Shane Warne, Glenn McGrath and Mitchell Johnson.

In January 2017, Hazlewood recorded an unusual innings in the first ODI against New Zealand. He had a 26-minute lo