Dowsett began his career at the Maldon and District Cycling Club in the City of Chelmsford. His talent was soon recognised and Dowsett became part of the British Olympic Academy development team. He won the under-23 version of the British Time Trial Championships in 2008 and 2009. In 2010, he rode for American team and won the under-23 European time trial championship. He also won a silver medal in the Time Trial at the 2010 Commonwealth Games.