Beckett Sennecke was born in Toronto, Ontario, Canada. In 2021-2022 Sennecke played in the GTHL U16 league for the Toronto Marlboros and was dominant scoring 35 goals and 45 assists in 45 games. He was then selected by the the Oshawa Generals of the OHL to play in 2022-2023. In his rookie season in the OHL he tallied 20 goals and 35 assists in 61 games. In 2022-2023, he also played in the WHC-17 for Canada White U17 and had 3 assists in 5 games.
Sennecke improved his numbers this past season for the Generals, averaging more than a point a game and helping to lead the team when former 1st round pick Cal Ritchie was injured. He ended the season scoring 27 goals and 41 assists in 63 games and continued to ascend on scouts draft boards.