Cracknell began rowing whilst attending the independent Kingston Grammar School and rowed at the Junior World Championships in 1989 and 1990, winning a gold medal in 1990. He graduated from the University of Reading as a Bachelor of Science (BSc) in Human Geography in 1993, followed by a PGCE at the Institute of Education and a Master of Science (MSc) from Brunel University in 1999. Moving into the senior squad, Cracknell made numerous appearances in the World Rowing Championships; however, he did not win any medals prior to the 1996 Summer Olympics. He qualified in the double scull for the 1996 Games, but fell ill with tonsillitis and was unable to race. In 1997, he won a seat in the men's coxless fours, with Steve Redgrave, Matthew Pinsent and Tim Foster. With this crew, he won the World Rowing Championships in 1997, 1998 and 1999 (with Ed Coode replacing the injured Foster), and finally the gold medal at the 2000 Summer Olympics. In August 2000, the month prior to winning gold in Sydney, he took part in a 3-part BBC documentary entitled Gold Fever. This followed the coxless four team in the years leading up to the Olympics, including video diaries recording the highs and lows in their quest for gold.