Walker is best known for winning the Olympic Games 1500 metres in 1976. Unfortunately, this achievement was somewhat overshadowed because 22 African countries boycotted the games to protest against a tour of South Africa by the New Zealand national rugby team.
Walker also held the world mile record with a time of 3:49.4 minutes set at Göteborg on August 12, 1975, bettering the previous time set by Filbert Bayi.