The aim of this paper was to study of the effect of different levels of dyslexia on parental stress in mothers with children dyslexic. The method is descriptive and type of causal or ex post facto research. The study population included mothers with children dyslexic referred to Specific Learning Disorders Center of Shahid Beheshti University and Tohid Psychological Services Center were from which 72 people with stratified random sampling were selected. The data were collected through the Reading Disorder Test and Parental Stress Index (PSI) and then analyzed by one-variable analysis of variance (ANOVA), multivariate analysis of variance (MANOVA) and scheffe test. Results: The results indicated that general parental stress rate and in both child and parent subscale in mothers with dyslexic children was higher than the cutting score. Conclusion: Difference of general parental stress among the mothers with dyslexic children of levels mild, moderate and severe was significant. Difference of parental stress in child subscale among the mothers with dyslexic children of levels mild, moderate and severe was significant. Difference of parental stress in parent subscale among the mothers with dyslexic children of levels mild with moderate and severe was significant. But the difference of parental stress in parent subscale among the mothers with dyslexic children of levels moderate with severe was not significant.