The cancer care charity – which relies almost entirely on voluntary donations – has been made aware of phone calls to people asking for bank details.
It urges anyone who gets a call to report it immediately to the police.
Maggie’s social media channel said: “ “We have received reports that people are making phone calls pretending to be from Maggie's and asking for bank details.
"This is not something we would ever do.”
Calls can also be reported to @actionfrauduk on 0300 123 2040.