Mitchell Marsh's talent and potential were noticed by national selectors early on. In 2010, at age 19, he earned his first call-up to the Australian Under-19 squad for the U-19 World Cup. He continued putting in solid performances for Western Australia, winning the state Player of the Year award in the 2013-14 season.

Marsh finally earned his long-awaited baggy green in 2014 when he made his Test debut for Australia against Pakistan in Dubai at age 22. He scored an unbeaten 87 in the fourth innings on a deteriorating pitch to help Australia draw the match. His first Test century (148 runs) came in 2015 against the West Indies in Jamaica.

Over the next few years, Mitchell Marsh became an irregular member of the Australian Test squad, often in and out of the playing XI.

Marsh didn't find sustained success in ODIs either, appearing in only 36 matches for Australia from 2011 to 2020 with a best of 76 runs. He was, however, part of Australia's 2015 World Cup winning squad though he played just one match in that tournament.

In 2020 and 2021 T20 World Cup finals he played an integral role in helping Australia reach the finals of the 2010 and 2021 T20 World Cups. Overall, Marsh has scored over 1400 runs and taken 30 wickets in 67 T20I matches for Australia since 2011.

At the domestic level, Mitchell Marsh has been a consistent performer and leader for Western Australia and Perth Scorchers in the Big Bash League over the years. He captained the Scorchers to their fourth BBL title in the 2021–22 season.

2022 marked a resurgence in Marsh's Test career. After being dropped in 2019, he was recalled for Australia's tour of Pakistan. He was awarded the Player of the Match performances in the first two Tests, scoring twin half-centuries in each.

Marsh consolidated his Test spot thereafter, delivering several crucial knocks during the 2022-23 home summer against West Indies and South Africa.