The purpose of the current study is to determine the extent to which adolescents’ irrational beliefs are predicted by their personality characteristics and stress coping approaches and to investigate whether adolescents’ irrational beliefs vary significantly depending on gender and parents’ education level. The population of the study is comprised of 5120 high school students attending the high schools in the Menteşe district of the city of Muğla in 2019-2020 school year. The sample of the study consists of 512 students selected from among the population by using the stratified sampling method. As the data collection tools, an information form to collect demographic data about the students, the Irrational Beliefs Scale-Adolescent Form, the Five-Factor Personality Inventory and the Scale of Stress Coping Styles, were used in the current study. Hierarchical multiple linear regression analysis was conducted to determine the extent to which the adolescents’ personality characteristics and stress coping approaches predict irrational beliefs and three-directional variance analysis was conducted to determine whether the adolescents’ irrational beliefs vary significantly depending on gender, mother’s education level and father’s education level. As a result of the study, it was concluded that of the personality characteristics, the sub-dimension of “neuroticism” is a positive predictor and the sub-dimensions of “openness to experience”, “agreeableness” and “conscientiousness” are negative predictors and of the stress coping approaches, the sub-dimension of “desperate approach” is a positive predictor, while the sub-dimensions of “optimistic approach” and “seeking for social support” are negative and significant predictors of the irrational beliefs of the adolescents. While the adolescents’ irrational beliefs were found to be not varying significantly depending on gender, mother’s education level and father’s education level, they were found to be varying significantly depending on binary interaction of gender x father’s education level. While in the male adolescents, the irrational beliefs were found to be decreasing with the increasing education level of the father, this is not true for the female adolescents.