Background: Multiple Sclerosis (MS) with four different types is one of the well studied autoimmune diseases of the central nervous system. Generally, two-thirds of MS patients are females who are at risk of pregnancy-related complications. Inappropriate responses of mother’s immune system, such as antibody production against placental proteins, may lead to pregnancy-related disorders. The association between pregnancy complications and some autoantibodies including anti-phospholipid and anti-angiotensin II type-1 receptor antibodies are clear examples in this regard. Objective: To investigate the probable placental antigens that might be targeted by the antibodies in the sera of MS patients. Methods: Total placental proteins were extracted from normal fresh placentas and were separated using two-dimensional gel electrophoresis (2-DE) technique. The separated proteins were transferred onto a Polyvinylidene Fluoride (PVDF) membrane and blotted with the pooled sera of MS women or healthy controls (20 individuals in each group). The differentially blotted spot was identified by mass spectrometry and confirmed by western blot technique. Results: The results indicated that the women afflicted with MS had an antibody against placental HSP70kDa protein 5 (GRP78). Conclusion: In the present study, a new placental autoantigen candidate, which was targeted by antibody present in MS women sera, was found. The clinical importance of this finding regarding pregnancy complications in MS patients should be investigated by further experiments.