Among the items stolen were more than a dozen Christmas hampers put together by pupils from St James Catholic School and who delivered the colourful packages last week after the school put on a walkathon to help bring in donations.
Speakers used by the Cailin Traditional Irish Dancing School, which stores its sounds system at the church, were also stolen.
Grantham said they believed the theft took place some time between 10pm on Saturday and 7am yesterday.
The mess was only discovered about 9.30am after someone there for morning Mass noticed it.
She said it appeared the thieves used a chair - put on top of a table and propped up against the wall divider - to remove louvres near the ceiling, to get into the locked room.
The mess left behind at the St Patrick's Cathedral on Broadway Ave in Palmerston North. Photo / Supplied
The door was found smashed to pieces.
They had already started distributing hampers to families in the community who needed them the most.
But more people tended to come forward asking for help as Christmas neared, Grantham said.
"It's not only food people need. Sometimes we get requests for nappies and petrol vouchers.
"We just get the items required [for each family] and give it out."
Senior Sergeant Darren Paki said they were asking for anyone who saw anything suspicious in the area between Friday afternoon and Sunday morning to come forward.
"The theft of donations means less for these families at what is already a hard time of year," he said.
"We would like to hear from anyone who saw something or who has information about those involved."
• Can you help? Anyone with information should get in touch by phoning 105
