Background & Objective: Adolescence is a crucial period in the human developmental cycle. The profound psychological, physical and social changes that occur during this period distinguish adolescence from other humans’ developmental periods. Adolescents are prepared at this stage in human development to enter an adult education and deal with life issues. From the range of teens' problems, depression is a disruptive mood disorder that can lead to many problems in their lives. The prevalence of adolescent depression may be higher among adolescent girls compared to boys. Sexual changes and identity– related questions and challenges, along with their need to gain independence from childhood dependencies, cause some adolescents to experience different social maladjustments during this period. These maladjustments, in addition to family tensions, have been influenced by the type of interactions among students through the spread of other social environments, especially in school, and may include issues such as maladjustment with classmates and teachers, academic failure, leaving school, anxiety and decreased self– esteem. For this reason, social adjustment is one of the variables that can be taken into consideration in the direction of assistance to depressed student girls. Accordingly, this study aimed to determine the effect of positive Mindfulness Therapy, Mindfulness– Based Cognitive Therapy and Cognitive– behavioral Therapy on social adjustment in female students with depression. Methods: The research method was semi– experimental, and research design was four groups with two stages (pretest and post– test design). To carry out the research, from 400 first secondary school female students with depression in Naein city (Yazd province, Iran) in 2017, 60 female students were selected Based on criteria of entry and exit. Then randomly assigned in four groups; including three groups of positive Mindfulness Therapy, Mindfulness– Based Cognitive Therapy and Cognitive– behavioral Therapy (each group with 15 persons) and control group (with 15 people). Social adjustment questionnaire was used to measure the dependent variable in the pretest and post– test. The group of positive Mindfulness Therapy, Mindfulness– Based Cognitive Therapy, and Cognitive– behavioral treatment received 12 sessions of treatment, and the control group did not receive any treatment. The data were analyzed by analyzing the pre– assumptions for the normal distribution of data, equality of error variance, regression line slope and equality of variance– covariance matrix by multivariable analysis of covariance. Data analysis was done using SPSS 21 software. Results: Descriptive findings showed that in the overall social adjustment, the Mindfulness– Based Cognitive– Therapy group had a mean of 36. 5 in the pretest phase and in the post– test phase, the mean of this variable changed to 17. 7. In the positive Mindfulness Therapy group, the mean of overall social adjustment in the pretest phase was 48. 1, and in the post– test phase, it changed to 3. 1. In the Cognitive– behavior Therapy group, the mean of overall social adjustment in the pretest phase was 35. 97, and in the post– test phase, it changed to 7. 53. In the control group, the mean of overall social adjustment in the pretest phase was 38. 6 and in the post– test phase, it changed to 34. 87. In four research groups, three components of social adjustment, emotional adjustment and academic adjustment were changes in the direction of changes in overall social adjustment. Results of multivariable analysis of covariance showed that there was a significant difference between the positive Mindfulness Therapy, Mindfulness– Based Cognitive Therapy and Cognitive– behavioral Therapy and control groups in social adjustment and their components (social adjustment, emotional adjustment and scholastic adjustment) in post– test after controlling for pretest (p<0. 001). Also, there was a significant difference between positive Mindfulness Therapy with Cognitive– behavioral Therapy in scholastic adjustment and total of social adjustment. Conclusion: Positive– Mindfulness treatment as a modern and valid treatment can be used alongside other treatments to help depressed student girls and their families, and in particular to promote the social adjustment of these girls. Therefore, at the practical level, it is necessary, first, to provide accurate information in girls' schools about the possibility of solving the problems of social adjustment of depressed student girls to school administrators, teachers, counselors and families. At the level of psychological treatment centers, also it is necessary to use positive– Mindfulness Therapy along with other mental treatments for depressed girls who have a problem of social adjustment and refer to these centers through schools or families. In sum, the results of this study by documenting the effect of positive– Mindfulness Therapy suggest that this new and combined therapeutic approach has significant potential for the treatment of mood disorders in adolescents.