Hewitt first played mixed doubles with his mother,
Lynn Hewitt. Lynn and Dean together played as the Australian national mixed doubles curling team at the
2017 World Mixed Doubles Curling Championship and the
2018 World Mixed Doubles Curling Championship At the
2019 World Mixed Doubles Championship, Hewitt and his new teammate
Tahli Gill made it to the semifinals before being eliminated by Sweden's
Anna Hasselborg and
Oskar Eriksson. In the bronze medal match, they again lost to
John Shuster and
Cory Christensen from the United States. Their fourth-place finish was the best finish ever for an Australian team at any World Curling Championship to that point. Gill and Hewitt were qualified for the
2020 World Mixed Doubles Championship, but the event was cancelled due to the
COVID-19 pandemic. At the
2021 Olympic Curling Qualification Event in December 2021, Gill and Hewitt made history when they won qualification to the mixed doubles tournament at the
2022 Winter Olympics. They are the first ever Australian curling team (in any curling discipline) to qualify for the Winter Olympics. At the Olympics, they finished with a 2–7 record, finishing in 10th place. Gill and Hewitt would continue to find success in mixed doubles in the next Olympic quadrennial from 2022–26, performing well on the mixed doubles curling tour and consistently being ranked as one of the top 5 teams in the world. They would also notably win a bronze medal at the
2025 World Mixed Doubles Curling Championship. This success would allow them to compete in the
2025 Olympic Qualification Event in the hopes of representing Australia at the
2026 Winter Olympics. Gill and Hewitt would finish round robin play with a 6–1 record, qualifying for the playoffs, but would lose to South Korea's
Kim Seon-yeong and
Jeong Yeong-seok 10–5 in the final qualification game, failing to reach the Olympics. However, Gill and Hewitt would bounce back at the
2026 World Mixed Doubles Curling Championship, where they would finish 8–1 after the round robin and after beating Italy in the semifinals, would go on to defeat Sweden's
Therese Westman and
Robin Ahlberg 8–4 in the gold medal game to win their first world championship, as well as the first world championship title in curling ever for Australia. ==Personal life==