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. Millman made his return at the Mestre Challenger in May, losing in the first round. 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. At Wimbledon, Millman drew Rafael Nadal in the first round and was easily beaten in straight sets. 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. In September, Millman made his Davis Cup debut in the world group semi-final against Belgium. Millman lost to world number 12 David Goffin. Millman then reached the quarter finals or better in five consecutive Challengers across Asia, winning Hua Hin. Millman ended 2017 with a singles ranking of 128.