St John says it is shocked and disgusted that a person stole items from an ambulance while paramedics were helping a patient.
A GPS unit, portable radio and personal items were stolen from the vehicle on Thursday in the Auckland suburb of Papatoetoe.
District operations manager Steve Walker says the ambulance was unlocked on the road while officers were helping a man inside the house.
Mr Walker says it is making the organisation question whether it needs to lock the vehicles, which he believes would take up vital time while treating a person.
Mr Walker says St John is just thankful that vital and expensive equipment such as a defibrillator was not taken.
He is urging the person who stole the items to return them to police.