McLeod was a promising high school athlete, running for Manchester High School and later Kingston College; during his early career, he competed in both the 110 m hurdles and the 400 m hurdles. He represented Jamaica at the 2011 World Youth Championships in Lille, qualifying for the finals in both hurdles events; he placed fourth in the 110 m hurdles and eighth in the 400 m hurdles. At the CARIFTA Games he won gold in the under-20 400 m hurdles in three consecutive years (2011, 2012 and 2013); he scored an additional five medals in the 110 m hurdles and the 4 × 400 m relay, including a relay gold in 2013. He also won gold in the relay at the 2012 CAC Junior Championships in San Salvador.
In 2013, his final year in high school, McLeod set Jamaican junior records in both the 110 m hurdles (13.24) and the 400 m hurdles (49.98) at the Boys and Girls Championships; he was the first Jamaican high schooler to break 50 seconds at the longer distance. After graduating from Kingston College he went to the University of Arkansas on a track and field scholarship.
McLeod had no experience running indoors before his move to the United States, but he adapted rapidly; he won the 60 m hurdles as a freshman at the 2014 NCAA indoor championships in Albuquerque, running a personal best 7.57 in the heats and 7.58 in the final. Outdoors, he placed second in the 110 m hurdles at both the Southeastern Conference (SEC) championships and the West Regionals, but pulled a hamstring at the NCAA championships and missed the final.
McLeod returned to competition in 2015; he won the SEC indoor title in a personal best 7.49. At the 2015 NCAA indoor championships he repeated as champion, running 7.55 in the heats and 7.45 in the final; his time in the final was a new Jamaican indoor record, broke Reggie Torian's NCAA record from 1997 and tied with Cuba's Orlando Ortega for the world's fastest time that winter. Outdoors, McLeod set a personal best of 13.21 at the Drake Relays and won at both the SEC meet and the West Regionals. He entered the NCAA outdoor championships in Eugene as the favorite; he won, running 13.08 in the heats and 13.01 in the final, but both times were wind-aided. Only one collegiate athlete, Renaldo Nehemiah in 1979, had run faster in any conditions. In addition to his hurdles victory, McLeod ran on the Arkansas relay teams in both the 4 × 100 m relay and the 4 × 400 m relay; Arkansas won the 4 × 100 m in 38.47 and placed sixth in the longer relay.
After the 2015 collegiate season McLeod turned professional and signed an endorsement deal with Nike, forgoing his two remaining years as an NCAA athlete; although he stayed at Arkansas to complete his business studies, he lost his eligibility to represent the Arkansas Razorbacks.
McLeod won the 110 m hurdles at the 2015 Jamaican Championships, defeating national record holder Hansle Parchment in a wind-legal 12.97 and breaking 13 seconds for the first time; the time was world-leading for a week. He made his debut as a professional at the István Gyulai Memorial in Székesfehérvár on 7 July, but pulled up with a cramp and failed to finish.