Alex Hill won gold with the men’s four at the 2011 Junior World Championships in Eton. He went on to win two silver medals at the 2012 and 2013 U23 World Championships in the men’s eight and pair respectively. Hill also contested the senior World Championships in 2013, taking out the B final in the men’s eight. Hill competed for South Australia at the 2013 Australian Youth Olympic Festival and had the honour of lighting the cauldron at the Opening Ceremony. In 2016, Hill was named in the Men's Four alongside Josh Booth, Josh Dunkley-Smith and Will Lockwood and raced at the 2016 Rio Olympic Games where he won an Olympic silver medal. In 2017, he was named in the Men's Four, with Josh Hicks, Jack Hargreaves and Spencer Turrin. He went on to win gold in the Men's Four at the 2017 World Championships, the first time in 26 years that Australia had won the boat class. In 2018, Hill was once again named in the Men's Four, where he raced at World Cups 2 and 3, winning gold. He raced in the same boat class at the World Rowing Championships in 2018, winning back-to-back world titles and was later named, with his crew mates, 2018 Male Crew of the Year by World Rowing. He also won the Grand Challenge Cup, stroking Australia's Men's Eight at the 2018 Henley Royal Regatta. At the Tokyo 2020 Olympic Games, held in July 2021, Hill won an Olympic Gold Medal as the Stroke of the Australian Men's Four. He joined crew mates Spencer Turrin, Alexander Purnell and Jack Hargreaves for a famous victory that broke Australia's run of three consecutive Olympic Silver Medals in this boat class. Further, the result came almost 25 years to the day since Australia last won gold in this race at Atlanta 1996. Hill's favourite place to row is Murray Bridge in South Australia. In November 2020 Hill was honoured by the Mayor of Loxton with the naming of Alexander Hill Drive in his hometown of Loxton, South Australia. In an acknowledgement of his athletic achievements, Hill was named 2021 South Australian Athlete of the Year.

For the 2022 international season, Hill was selected as the A.R.T. Men’s Single Scull representative.  However, due to some injury challenges faced during the European tour, Hill teamed up with Harley Moore to win a Silver Medal in the Men’s Coxless Pair at the World Cup III regatta held in Lucerne, Switzerland.

At the 2022 World Rowing Championships, held in Racice, Czech Republic, Hill and Moore qualified for the A Final and finished fifth.