Embryonic stem cell research is considered one of wonderful developments in medical arena and scientific achievements contributing to the treatment of many diseases. Due to its important legal consequences, its analysis of vital importance. One of the theories proposed to justify the research is Medical Self-Defense. This theory purports that when a disease attacks a person and there is no escape from its risk, similar to the traditional self-defense in criminal law, one can obviate the source of threat and claim the right to live. Therefore, any research to promote methods to counter any immedicable disease becomes legitimate. Considering the fact that in embryonic stem cell research embryo is destroyed as third-party while in traditional self-defense one cannot destroy (or kill) a person who is not the source of threat. As a result, fundamentals of this theory are disputable. Furthermore, this theory opposes the dignity of embryo.