The objective of this study was to compare family functioning, cognitive emotion regulation strategies and academic performance of female students with and without oppositional defiant disorder (ODD) by controlling birth order in students of primary schools of Ahwaz City. The study type was causal-comparative. The population for this study was female students in the sixth grade of primary schools of Ahvaz who were enrolled in the academic year 2014-2015. From this population, a sample of 50 students with oppositional defiant disorder (ODD), were selected by multistage random cluster and simple sampling methods and the same number were selected from students without ODD. To collect the data, Child Behavior Checklist (parent form), the Family Assessment Device of Epstein, Baldwin and Bishop, Garnefski Cognitive Emotion Regulation Questionnaire and to determine the academic performance, Grade Point Average were used. MANCOVA results showed that there is significant differences in family functioning, cognitive emotion regulation strategies and academic performance between female students with oppositional defiant disorder and students without ODD. ODD students had lower performance in family functioning, positive cognitive emotion regulation strategies and academic performance than students without ODD, but were higher in negative cognitive emotion regulation strategies.