[4][5][non-primary source needed] In January 2019, Millman received the OLY post-nominal title at the Brisbane International tournament.

He won the F8 Futures in Australia, was runner-up at an F1 in Romania losing to Răzvan Sabău and made the semis of a Morocco F5 tournament.

He won his second Futures event in Kalgoorlie defeating Matthew Ebden and made the second round of qualifying at the Australian Open.

Millman was again awarded a wildcard into the 2011 Brisbane International main draw where he lost to fellow Australian Matt Ebden.

He then competed in Challengers spread across Asia, Australia and Europe before injuring his shoulder during an Italian futures tournament in April.

Millman began 2013 at the Brisbane International where he entered qualifying and recorded straight set wins over Luke Saville, Alex Bogomolov and Donald Young to make it into the main draw.

Following an impressive performance at the Brisbane International, an Australian writer/sports physiologist coined the term 'Millminions' to describe Millman's extensive and loyal fans base.

Millman received a wildcard entry into the Apia International Sydney and defeated Tommy Robredo in the first round.

Millman was awarded a wild card into the French Open but on 20 May 2013, he announced his withdrawal due to a shoulder injury.

Millman was replaced by countryman and rising star Nick Kyrgios who previously had a wildcard for qualification rounds.

[17][non-primary source needed] It was later announced that his first competition in eleven months would be the Chengdu China F4, commencing on 7 April, where he made the quarter-final.

In September, Millman made the semi-final of the Sacramento Challenger, losing in three sets to world number 54 Sam Querrey.

In June, Millman secured his first Grand Slam main draw entry via qualifying for the first time in his career at Wimbledon.

He defeated Ričardas Berankis without losing a single game in the first round, marking this the first time in Olympic tennis history that any player won a match in such fashion.

Millman was given a wildcard into the 2017 Brisbane International but withdrew prior to the tournament with a hip injury, which sidelined him for the first five months of the season.

At the French Open, just one week after re-joining the tour, Millman lost to 17th seed Roberto Bautista Agut in four sets.

Following his exit at Roland Garros, Millman went on to compete in three Challenger events in the lead up to Wimbledon, but failed to make it past the second round in any tournament.

After little success since returning from injury, Millman had a breakthrough at the Lexington Challenger in August, making it to the final before being defeated by Michael Mmoh in three sets.

At the US Open, Millman produced his best tennis of the season to upset fellow Aussie Nick Kyrgios and Malek Jaziri to progress to the third round, where he eventually lost to Philipp Kohlschreiber.

He defeated Peter Polansky in round one and had two match points against world number 3 Grigor Dimitrov before losing in three sets.

In February, Millman won the Kyoto Challenger, the tenth of his career, propelling him back into the world's top 100 after a 12-month absence.

[32] In September, Millman pulled off a huge upset by defeating the second seed Roger Federer in the fourth round of the US Open, in four sets.

This was Millman's first win over a top-ten player and saw him advance to his first Grand Slam quarterfinal, where he lost to eventual champion Novak Djokovic in straight sets.

However, he found form at Wimbledon, progressing to an equal career-best 3rd round with victories over Hugo Dellien and 31st seed Laslo Djere before falling to Sam Querrey in straight sets.

At the Japan Open, Millman made his way to the finals, where he faced Novak Djokovic, but finished short of winning his first ATP title by losing in straight sets.

Millman began his season at the ASB Classic in Auckland where he defeated Michael Mmoh and Karen Khachanov to make the quarter-finals against eventual runner-up Benoît Paire, who he lost to in three sets.

At the 2021 Sofia Open he reached his fourth quarterfinal for the season (after Munich, Washington and Astana in Nur-Sultan), and for a second year in a row at the tournament, where he lost to Marcos Giron in 70 minutes.

Millman was aiming to reach his first tour-level semifinal since Astana in 2020, where he won his maiden ATP Tour trophy.

Millman revealed in early 2012 that support he received while injured and contemplating retirement in 2011 gave him the drive to continue pursuing tennis as a career.

Following his match against Andy Murray, the hashtag term '#Millman' began trending worldwide on Twitter for several hours.