Starting with athletics at age 17, Crawford debuted internationally in 1970, winning a bronze medal in the 100 m at the Commonwealth Games. Only two years later, he surprisingly qualified for the final of the Olympics in Munich, although he had to forfeit that race after 20 m due to an injury.
In 1975, Crawford was added to the team of American coach Bob Parks, who prepared Crawford excellently for the 100 m and 200 m events at the Montreal Olympics, running only a few races during the season. The tactics paid off, as Crawford won the 100 m, narrowly in front of Don Quarrie of Jamaica, winning Trinidad and Tobago's first Olympic gold medal. He had also qualified for the 200 m final, but pulled out due to an injury.
Hasely Crawford´s last success was a bronze medal in the 1978 Commonwealth Games (100 m). He did also participate in the 1980 and 1984 Olympics—the most participations for an Olympian of Trinidad and Tobago—but didn't reach to a final again.
A national hero in his home country, Crawford has appeared on postage stamps and has an airplane and a sports stadium named after him.