[2][3] In December 2015, Mitchell withdrew from the final round of the 2016 Australian Open Main Draw Wildcard playoff to be present for the birth of his daughter.

[4] Mitchell competed in his first junior ITF under 18 event in December 2005 as a 13-year-old, he was beaten soundly in the first round by James Wong 6–3 6–1.

Tennis Australia provided wildcards into the Traralgon International and the Australian Open junior event and Mitchell did not disappoint.

Following his successful Australian summer Mitchell won his first and only junior title in Nonthaburi, Thailand where he defeated Suk-Young Jeong in the final 7–5 6–3.

In the last event Mitchell ever entered he recorded his best result as he went through qualifying to reach the final of the 2010 Junior Wimbledon Championships where he lost in straight sets to Márton Fucsovics 4–6 4–6.

At the 2011 Australian Open, Mitchell received a wild card into the Men's Doubles along with James Duckworth, but they were defeated in the first round by Daniel Nestor and Max Mirnyi.

Mitchell began his year at the 2014 Brisbane International in qualifying where he defeated seventh seed Wayne Odesnik in the first round in straight sets.

Mitchell partnered with Jordan Thompson in the Men's Doubles where they won their first round over Carlos Berlocq and Alejandro González in three sets.

In late February, Mitchell made the second round of the Shimadzu Challenger where he won the doubles with Jordan Thompson.

Mitchell won his first Challenger tournament, the Canberra International, defeating compatriot Luke Saville in the final 5–7 6–0 6–1.

He made the second round of qualifying for the 2016 Australian Open and the quarter-final of the Launceston Challenger before heading to Asia and North America.

Mitchell told Tennis Australia "It’s early days, my first tournament back, but obviously I’m refreshed mentally" adding "I feel like I want to be here and I want to do well, so there’s obviously been a big change in mindset".