Brownlee represented Great Britain at the 2008 Beijing Olympics in the triathlon, finishing in 12th place and first British competitor. During the 2008 season, his best world cup finish was 3rd place in Madrid and he also won the under-23 world championship. He convincingly won the 2012 London Olympic Games triathlon in 1 hour, 46 minutes, 25 seconds. His brother Jonathan Brownlee finished third in the same event.
Brownlee won the 2009 ITU Triathlon World Championship – winning all five of the season's ITU World Championship Series events in which he competed. He was victorious in Madrid, Washington D.C, Kitzbühel and London before winning the 2009 season Grand Final, held on Australia's Gold Coast on 12 September and thereby became the first person ever to win the ITU world Triathlon titles for Junior Men (2006), Under 23 Men (2008) and Senior Men (2009).
Alistair went on to also win the 2011 ITU world title after winning the Grand Final in Beijing.
- 7 Times Yorkshire Cross Country Champion U13 – Senior
- 7 Times Yorkshire fellrunning champion
- 2006 Junior European Duathlon Champion
- 2006 Junior World Champion
- 2007 Junior European Champion
- 2007 Junior World Vice-Champion
- 2008 U23 World Champion
- 2009 Hyde Park Triathlon Champion
- 2009 British National Elite Duathlon Champion
- 2009 ITU World Champion
- 2010 ETU European Champion
- 2011 ETU European Champion
- 2011 ITU World Champion
In the six years from 2005 to 2010, Alistair Brownlee took part in 31 ITU competitions and achieved 24 top ten positions, among which 13 gold medals, 5 silver medals, and 2 bronze medals.
- 2008, won the U23 World Championship and placed 12th at the Olympic Games in Beijing
- 2009, won the Dextro Energy World Championship Series placing first in almost all of the circuit's triathlons (i.e. Madrid, Washington DC, Kitzbühel, London, and Gold Coast)
- 2010, opened the season with the European Championship gold medal but subsequently had to put up with a stress fracture of the femur
- 2011, won the World Championship Series triathlons in Madrid and Kitzbühel, leading the ITU World Championship ranking, and crowned himself again European Elite Champion