Cognitive biases can cause diverse medical errors and lead to malpractice with potential harm to patients. Some cognitive biases are due to social behavior, professional specialization, and personal experience, leading to commission or omission in medical conduct. We would like to propose a previously undescribed cognitive bias called "Schrödinger's cat bias." In 1935, Erwin Schrödinger proposed a dual system based on quantum mechanics that a cat could be dead or alive at the same time. The "Schrödinger's cat bias" is a situation in which a physician takes a decision and requests an exam or procedure that was unnecessary and puts the patient through an unforeseen risk. After the procedure, if there is a good outcome, the patient will be grateful for it. However, if there is a bad outcome, he would still be grateful for their efforts in trying to find the etiology. This cognitive bias will, most of the time, favor the therapies over the decision of not to treat.