[23] Brownlee represented Great Britain at the 2008 Summer Olympics in the triathlon event, finishing in 12th place and first British competitor.

[26] During the 2010 off season, Brownlee sustained a stress fracture of the femur and was not able to return to competition until June, which made defence of his ITU title almost impossible.

In the April opening event of the 2011 ITU Championship season in Sydney, Brownlee suffered a heavy fall while in the lead which brought early disappointment and a 29th-place finish.

[30] This was contrasted with outstanding success when, in the space of just twenty-one days during June 2011, he convincingly won the next two ITU series events (in Madrid[31] and Kitzbühel[32]) and, following a puncture whilst in the lead and having to make up more than 30 seconds on the new leaders, successfully defended his European title at the 2011 Pontevedra ETU Triathlon European Championships and shared the podium with his brother Jonathan, who took the silver medal.

Brownlee won the Commonwealth Games Triathlon in 2014, controlling the race with his brother from the start, before pulling away on the first lap of the run in dominating style; Jonathan took the silver medal.

[36] Brownlee also took gold in the mixed triathlon team relay at the 2014 Commonwealth Games, with brother Jonathan, Vicky Holland and Jodie Stimpson.

Alistair abandoned his own chance of winning the race, instead opting to assist his brother over the line, finally pushing him to a second-place finish and coming in third himself.

[38] Brownlee made his long-course debut at the half-iron distance Challenge Mogan-Gran Canaria triathlon in April 2017, which he won in a time of 4:03:09, finishing over eight minutes ahead of the runner-up.

Key: BG = British Gas (the sponsor); DNF = Did not finish; DNS = Did not start; U23 = Under 23 In 2010, only the femur fracture could slow Brownlee's dominance for some time.

At the Grand Final in La Baule (Triathlon Audencia, 18 September 2010), Alistair placed 2nd, Jonathan 3rd, and their rival Javier Gómez Noya won gold.