Burglars broke into Mind in Mid Herts, in Hatfield Road, after smashing a window and forcing their way in some time between 2pm on Monday and 8.30am on Tuesday.
They sifted through all four of the charity’s offices and left with around £250 which had been collected at a fundraiser just days before the incident.
Chief executive Gloria Holland, who discovered the break-in when she arrived at work on Tuesday morning, said: “We had a community event at The Courtyard Cafe at the weekend, it was a lovely event and all the money was raised for the charity, and then on Monday someone breaks in and takes everything. I am really saddened by it.”
She added: “They have left such a mess, they have broken all or our cash tins and forced open drawers and filing cabinets.”
Due to the damage the charity had to cancel two of its services on Tuesday, including a drop-in session for people with mental health difficulties.
A spokesman for Herts Police said no arrests have been made and asked anyone with information to call the non-emergency 101 number.