At the end of his junior year, Hillman signed a two-year entry-level contract with the Blackhawks on March 27, 2018,[1] and made his NHL debut on March 30, 2018, in a game between the Blackhawks and the Colorado Avalanche.[5] Hillman recorded his first career NHL goal on April 4, 2018, in a game against the St. Louis Blues, to help the Blackhawks win 4–3.[6]
As an impending restricted free agent, Hillman was not tendered a qualifying offer by the Blackhawks, releasing him as a free agent on June 25, 2019.[7] With limited interest from NHL/AHL clubs, Hillman signed a one-year contract with the Toledo Walleye of the ECHL on July 26, 2019.[8] In the 2019–20 season, Hillman contributed with 13 points through 35 regular season games with the Walleye, while also leaving on loan on two occasions by signing two tryout contracts in the AHL with the Grand Rapids Griffins and Stockton Heat.
On January 20, 2021, Hillman extended his professional career by signing with the South Carolina Stingrays of the ECHL for the 2020–21 season.[9]
Following the 2021–22 season, having played with the Toledo Walleye in the ECHL and the Grand Rapids Griffins, Providence Bruins in the AHL, Hillman was signed to a one-year AHL contract with the Hartford Wolf Pack on July 6, 2022.[10]