After 4x100m Freestyle Relay silvers at the 2006 and 2007 European Junior Championships, Adam won silver in the 100m Freestyle at the 2008 British Champs to secure his debut Olympic spot in the 4x100m Freestyle Relay quartet in Beijing.
He backed it up with 50m and 100m Freestyle gold at the 2009 British Champs and his first World Championship appearance the same season in Rome.
Brown helped England win 4x100m Freestyle silver on his Commonwealth debut in 2010 and competed in the 50m and 100m Free as well as the 4x100m Free and 4x100m Medley Relays at the 2011 Worlds
As well as competing in the individual 50m and 100m Freestyle at London 2012, he swam the anchor leg of the 4x100m Medley Relay quartet as they finished fourth on the final day in London.
After finally grabbing the British 50m Freestyle record in 2013, Brown secured his best individual World Championship result, finishing ninth in the 100m Freestyle in Barcelona.