Prior to joining Toronto, Carbery served as head coach of Washington's American Hockey League (AHL) affiliate the Hershey Bears for three seasons from 2018 to 2021. Under Carbery, Hershey posted a combined record of 104-50-9-8 (.658 point percentage), including an AHL-best 24-7-2-0 record (.758 point percentage) in his final season behind the Bears' bench in 2020-21. Carbery received the Louis A.R. Pieri Memorial Award as the AHL's outstanding coach for the 2020-21 season, becoming the fifth coach in Hershey franchise history to win the award. During his three-year tenure with Hershey, Carbery coached and aided in the development of several players that appeared in games with the Capitals during the 2022-23 season, including Martin Fehervary, Aliaksei Protas, Connor McMichael, Alex Alexeyev, Beck Malenstyn, Lucas Johansen and Joe Snively.