Parkinson’s disease (PD) is one of the neurodegenerative disorders. Evidence suggests that estrogen may protect the nigrostriatal dopaminergic pathway from degeneration. However, estrogen has side effects. Plant-derived non-steroidal estrogens found in soy, may exert beneficial effects of estrogen without its unwanted side effects. The aim of this study was to evaluate the effect of soy isoflavones on muscular stiffness in an ovariectomized animal model of PD. Fourteen rats were divided to three groups: Control group (C) that was intact and fed normal diet, (U) group that was fed with normal diet after ovariectomy and underwent electrical lesion of SNc for 4 weeks, and (S) group that was fed with dietary soy meal after ovariectomy and underwent electrical lesion of SNc for 4 weeks. Then, muscular stiffness was examined by Morprogo test. One-way ANOVA and a paired student's t-test by SPSS software was used for statistical analysis. Muscular stiffness in U group significantly differed from C and S groups (p<0.001). There was no significant difference between C and S groups. Meals containing soy prevent from muscular stiffness due to SNc lesion in ovareictomized rats. Thus, the use of soy in menopause may be beneficial for prevention of muscular stiffness due to PD.