The purpose of this study was to develop a structural model of psychological well-being based on fear of negative evaluation mediating feelings of loneliness in adolescent girls with psychosocial problems. Methodology: The present study was applied in terms of purpose and in terms of quantitative method and survey-correlation method. The statistical population consisted of female adolescent students with mental health problems who were studying in the second grade of secondary education in Mashhad Nursing School District 2 in the academic year of 2017-18. The method was multistage cluster sampling, so that a list of all secondary schools for girls in the second district of Mashhad was composed of 24 schools that were classified as 4 schools per cluster with respect to government and nonprofit and number of students. One cluster was randomly selected and at the second stage of each school and at each grade level, a total of 3 classes from each school were selected and the students were given questionnaires. The tools of the present study were Psychosocial Well-being Scales (Ryff, 1980), Fear of Negative Evaluation (Leary, 1983), andDehshiri et al., 2008), Psychosomatic Complaints (Takata & Sakata, 2004). In the present study, SPSS software version 24 and SmartPLS2 software were used. Findings: The results showed that fear of negative evaluation with sense of loneliness had a positive relationship with psychological well-being and negative relationship with fear of negative evaluation with psychological well-being, according to GOF value of 0.595 indicating strong fit of model. It had a lot of research; it had some mediating effect. Conclusion:In order to improve the psychological well-being of adolescent female students, the present study demonstrates the importance of selfexpression planning and training and communication skills to reduce feelings of loneliness and screening of students with negative evaluation to provide appropriate psychological treatment for this group of adolescents. Reminds students of education.