Donohoe was born on 3 March 1995 in Nhulunbuy, Northern Territory. In 2009, at the age of fifteen, he injured his right bricep/triceps as a result of his arm getting caught in a rope whilst trying to jump into a creek from a tree. This led to limited use in his right arm. He attended Xavier College. He lives in Melbourne, Victoria.
He took up competitive cycling in 2010 after participating in rugby union, BMX and triathlon. His love of cycling was an outcome from his time as a triathlete in Darwin, Northern Territory. He competes in both abled bodied and para-cycling. It was Michael Gallagher who after noticing Donohoe's derformed arm suggested that he consider para cycling. In para-cycling, he is classified as C5. At the 2013, UCI Para-cycling Track World Championships, he won bronze medals in Men’s Time Trial C5 and Men’s Road Race C5. Competing at the 2014 UCI Para-cycling Track World Championships in Aguascaliente, Mexico, he won bronze medals in the Men's C5 1 km time Trial (1:03.788) and the Men's C-1-5 scratch race exhibition final. In 2014, at UCI Para-cycling World Championships in Greenville, South Carolina, he won the gold medal in the Men’s Road Race C5 and finished sixth in the Men’s Time Trial.
In January 2015, he finished third in the Mars Cycling Australia Road National Championships Under 23 Road Race at Buninyong, Victoria. At the 2015 UCI Para-cycling Track World Championships in Appledorn, Netherlands he won the gold medal in the Men's 15 km Scratch Race C5 and silver medals in Men's Individual Pursuit C5 and Men's 1 km time Trial C5.
At the 2015 UCI Para-cycling World Championships in Nottwil Switzerland, he won the gold medal in the Men’s Road Race C5 and silver medal in the Men’s Time Trial C5.
In January 2016, he finished fourth in the Mars Cycling Australia Road National Championships Under 23 Road Race at Buninyong, Victoria. At the 2016 UCI Para-cycling Track World Championships in Montichiari, Italy, he finished second to fellow Australian Michael Gallagher in the Men's 4 km Individual Pursuit C5. He also won the bronze medals in the Men's 1 km Time Trial C5 and Men's Scratch Race C4–5.
At the 2016 Rio Paralympics, he won silver medals in the Men's Individual Pursuit C5 and the Men's Road Time Trial C5. In the C4-5 road race he sensationally collided with Ukraine's Yehor Dementyev as they sprinted towards the finish line. The two leaders were jostling for victory in their 84 km event before Dementyev, later disqualified, veered into the path of the Australian and they both crashed to the ground. Donohoe ran across the line without his bike, a move which proved to be his undoing.
At the 2017 UCI Para-cycling Track World Championships in Los Angeles, United States, Donohoe won a silver medal in the Men's Scatch Race C4-5.
At the 2017 UCI Para-cycling Road World Championships, Pietermaritzburg, South Africa, he finished eighth in the in the Men's Time Trial C5 and seventh in the Men's Road Race C4-5.
In 2016, he is a Victorian Institute of Sport scholarship holder.2014 – Victorian Institute of Sport 2XU Youth Award for athletes under the age of 20.
2014 – Cycling Australia Elite Para-cyling Male Athlete of the Year.
2015 – Cycling Australia Elite Para-cyling Male Athlete of the Year.
2015 – Australian Institute of Sport Awards#AIS Para Performance of the Year