Shimron's cricketing journey began at a young age. He started playing tape ball cricket in his village, imitating West Indian legends like Curtly Ambrose and Courtney Walsh. At the age of 9, he began playing school-level cricket for the Rose Hall Estate Primary School and the Young Warriors Cricket Club.

Hetmyer's talent and potential were evident from an early age. He captained the Guyana Under-15 and Under-17 teams, and in 2014, at the age of 17, he was selected in the West Indies Under-19 World Cup squad. In 2016, he was appointed as the captain of the West Indies Under-19 team, leading them to their first-ever World Cup title in Bangladesh.

Hetmyer's domestic career began in 2014 when he made his first-class debut for Guyana in the Regional Four-Day Competition. His performances in domestic cricket earned him a call-up to the West Indies senior team, and he made his international debut in 2017.

In his ODI debut against New Zealand, Hetmyer scored 29 runs off 42 balls. He went on to become a consistent performer for the West Indies, scoring 5 centuries and 4 half-centuries in 40 innings. Hetmyer's Test debut came in 2017 against Pakistan, where he scored 11 and 21 runs in the two innings. While he has not been as consistent in Test cricket, he has shown glimpses of his talent, scoring 5 half-centuries.

Hetmyer's T20I career has been less successful, with an average of 16.41 in 20 matches. However, he has found success in domestic T20 leagues, including the Caribbean Premier League (CPL) and the Indian Premier League (IPL). In 2018, he became the youngest player to score a century in the CPL.