He began his 2015 season with a new national record of 20.15 seconds for the 200 m in March, placing second to Anaso Jobodwana at the Cayman Invitational. Hughes made his IAAF Diamond League debut in June at the adidas Grand Prix in New York, where he was commended for almost beating world champion Usain Bolt. His first British national title win came at the 2015 British Athletics Championships at the start of July, gaining him selection for the 2015 World Championships in Athletics. Wins over 200 m at the London Grand Prix and Athletissima meets moved him to the top of the Diamond League rankings. His new best of 20.05 seconds at the London meet also made him Europe's top ranked sprinter. He improved further 200 metres World Championships final in Beijing, recording a time of 20.02 seconds to place fifth while his clubmate Usain Bolt defended his world title.