[15][16] After playing just once for Queensland Academy, Labuschagne made his first-class cricket debut in the first round of the 2014–15 Sheffield Shield season against South Australia at the Adelaide Oval.

Opening the batting with Joe Burns, he scored 83 runs in Queensland's first innings, featuring in a 99-run fourth-wicket partnership with Nick Stevens.

[17] Later in the 2014–15 season, Labuschagne was used as a substitute fielder for the Australian national side in the second Test against India at the Gabba, taking a low catch at short leg.

[1] Labuschagne made his List A debut for Queensland in the 2015 One-Day Cup in October 2015 and scored his maiden first-class century in the following month, making 112 runs in his eighth Sheffield Shield match.

[22] In the 2024–25 Sheffield Shield season, Labuschagne switched from his part-time legspin to bowling medium pace in the lead-up to the Test series against India.

[24] He made 1,114 runs in his first County Championship season, including three centuries in his first four first-class matches - one of which was a then career-best 182 against Sussex in a Glamorgan record second-wicket partnership of 291.

[31][32] He made his Test debut for Australia against Pakistan on 7 October 2018, scoring a two-ball duck in his first innings and 13 runs in his second.

[34] Marnus was named in the Australian One Day International squad in December 2018 ahead of the team's tour of India the following year before he was surprisingly added to the Australian Test squad for the fourth Test match against the touring Indians at the start of the year.

[37] After showing good early season form for Glamorgan in county cricket,[38] he was named in Australia's squad for the 2019 Ashes series in England.

[48] Labuschagne retained his place in the Australian side for the visit of Pakistan the following summer, scoring 185, his maiden Test century, at the Gabba.

[54] He made his ODI debut on 14 January; Australia won the match by ten wickets with Labuschagne not batting or bowling in the game.

[56] After being retained in the Australian squad for their tour of South Africa, he scored his first ODI century in March, making 108 runs at Potchefstroom, close to his hometown.

[58][59] On 16 July 2020, Labuschagne was named in a 26-man preliminary squad of players to begin training ahead of a possible tour to England following the COVID-19 pandemic.

[60][61] On 14 August 2020, Cricket Australia confirmed that the fixtures would be taking place, with Labuschagne included in the touring party.

[71] He scored a match-winning half century in the World Cup Final against India to take his team home.

[77] They have a chocolate Labrador named 'Milo' who has been known to make appearances on Labuschagne's Instagram playing backyard cricket.

In preparation for the 2022 Australian tour of Pakistan, he was seen practising batting on his home balcony in Brisbane on a rubber mat laden with pieces of taped aluminium and metal sheeting to try to emulate the variable bounce and turn of Pakistani wickets.