Sillinger was selected 11th overall by the Medicine Hat Tigers of the Western Hockey League in the 2018 WHL Bantam Draft.

In 2020, due to the COVID-19 pandemic delaying the return of the Western Hockey League, the Tigers agreed to send Sillinger to the Sioux Falls Stampede in the United States Hockey League on a one-year loan agreement.

[4] On March 13, 2022, Sillinger scored his first NHL career hat-trick in a 6-4 win against the Vegas Golden Knights.

The family briefly resided in Phoenix, Arizona, St. Louis, Missouri and Garden City, New York, as Mike's career led him on to play for the Phoenix Coyotes, St. Louis Blues, and New York Islanders, respectively.

He was previously in a relationship with pop singer Tate McRae from late 2021 to early 2023.