Jaswant Singh Gill first played hockey while studying at school. After enrolling at college, he founded the college’s hockey team, taking charge of the team for two seasons. In 1959, he joined the Indian hockey team. The following year, Singh was selected to play for India at the 1960 Roma Olympics. He scored four goals at the Olympics and was part of the Indian team that won the silver medal. After the Olympics, he toured Ceylon with the national team.
Singh was also a member of the Indian Army, originally joining in 1949. In 1962, he fought in the Sino-Indian War at the disputed border in the Himalayas. Whilst in the Army, Singh met Dhyan Chand, who is considered to be the greatest hockey player ever. Singh eventually retired from the Army in 1987, reaching the rank of Lieutenant Colonel.