Pictures published Monday by l'Echo de Shawinigan show the top of the 93-year-old Cup bashed in and the two hockey player figurines on either side of the bowl missing. The newspaper said the wooden base was also cracked.
How the damage occurred was unclear. Each player on the championship team was allowed to have the Cup for 24 hours to celebrate in his home town.
The Cataractes won the Cup on home ice by defeating the London Knights in the junior hockey final in May.
The League commissioner Gilles Courteau issued a statement on Monday, condemning the Cup's apparent condition.
"The Memorial Cup was donated in 1919 to honour Canada’s war fallen," said Courteau. "It is unfortunate and deplorable to see it in such a state. The damages that were caused will be billed to the team."
League spokesman Photi Sotiropoulos said the Cup will be returned to the Canadian Hockey League, which will have it repaired.
There was no estimate on the cost of repairs. Winning teams that want to have the trophy over the off-season must take out $50,000 in insurance against damages.
It is not the first time the Memorial Cup has been damaged. During the on-ice Cup presentation after the 2008 tournament, the top of the trophy broke off in the hands of Spokane Chiefs captain Chris Burton as he was passing it to a teammate.
There were dents and nicks when other clubs had the Cup as well.
''It concerns us, but it is not something that is unheard of,'' said Sotiropoulos.
The Cup is not due for another public appearance until the Cataractes regular-season home opener on Sept. 21 against Drummondville.
There is a long history of championship trophies being damaged. In 1962, the Toronto Maple Leafs dropped the Stanley Cup into a bonfire. One of the worst was in 2011, when Sergio Ramos of Real Madrid dropped Spain's Copa del Rey off the top of a team bus, which ran over the trophy.