When Michel was 14 years old, he, his mother (Marianne Jazy) and his older sister (Alfreda) settled in Paris.

Marianne remarried; her new husband, a truck driver, moved the family into a 10-by-12-foot (3 × 4 m), one-room apartment on Rue Rodier in Montmartre.

Michel left school at the age of 14 and became a uniformed doorman and elevator operator at a bridge club near the Arc de Triomphe.

[4][5] Jazy won his first French national championship title in 1953 – the 1000 m race at the youth level (for those under the age of 18 years).

He won his second French national championship title in 1955 – the 1500 m race at the junior level (for those under the age of 20 years).

[4][5] In his first participation at the Olympic Games in Melbourne in 1956, Jazy clocked a time of 3:50.0 in the 1500 metres, which equaled his personal best but was not sufficient to reach the final.

In the final, Jazy ran the race of his life to obliterate his personal best time and set a new national record, finishing 18 metres and 2.8 seconds behind Herb Elliott.

He was ahead of the leading runner of the chasing pack by a body length 100 metres from the finish line.

Jazy won the race in a personal best and new European record time of 13:27.6 minutes, with Keino and Clarke finishing in second and third place, respectively.

[4][5] On 12 October 1966 in Saint-Maur-des-Fossés, Jazy won a 2000 metres race in 4:56.2 minutes, which was his ninth and last world record.