This study explored whether Emotion Regulation Styles have any mediating effects on the relationship between Parenting Behavior and Adjustment in School perceived by Middle School Students. To examine this, 375 male and female middle school student participants were asked to complete the questionnaires of Parenting Behavior, Adjustment in School and Emotion Regulation Styles. The statistical analysis program (SPSS 18.0) was used for analysing the collected data. from Pearson Correlation test, Stepwise Regression Analysis and Baron and Kenny(1986) are Presented by 3-steps model was used. Lastly, Sobel test was used to verify mediation effects. The main findings were as follow First, the findings in a correlation analysis indicated that parenting behavior, emotion regulation styles, adjustment in school were positively correlated. Second, in examining the influences of parenting behaviors and emotion regulation style to adjustment in school, influencing powers showed the following order of active style, father's affection, support-seeking style, mother's monitoring, over-expectation of mother's parenting behaviors, and father's physical abuse. Third, study results showed that the mediating effects of the emotion regulation styles in the relationship between parenting behavior and adjustment in school perceived by middle school students. parenting behavior as the predictor, active emotion regulation style as the mediator and adjustment in school as the outcome variable - were significant as a full mediation effect. Finally, we discuss the implications and limitations of this study and suggest future directions of this research.