Guy Learmonth's first major athletics competition was the 2011 European Athletics Junior Championships. He competed in the 800 metres event, winning his heat. In his semi-final, he finished fifth, a place which could have earned him a fastest loser spot, but the other semi-final was won in a time two seconds faster than Learmonth's race, meaning that both fastest loser qualifiers came from the second semi-final. He also competed at the BUCS Indoor Championships that year, winning the 800 metres by over a second and setting a new championships best performance. He won his first national senior medal in 2011, taking a bronze at the British Indoor Athletics Championships.