Purpose: In this study, the relationship between university students' self-esteem in decision-making and decision-making styles and intolerance to uncertainty, cognitive flexibility and the level of happiness were investigated. Research Methods: The study was conducted on 349 university students (69% female, 31% male) between the ages of 17-25 (average age 20.42). In this study, the Melbourne Decision Scale, the Intolerance to Uncertainty Scale, the Cognitive Flexibility Inventory and the Oxford Happiness Scale-Short Form were used to measure self-esteem in decision-making and decision-making styles and intolerance to uncertainty, cognitive flexibility and the level of happiness. Findings: Calculated correlations showed that there were significant relationships between university students' self-esteem in decision-making and decision-making styles and intolerance to uncertainty, cognitive flexibility and the level of happiness and were significantly predicted by the variables of intolerance to uncertainty, cognitive flexibility and happiness. Implications for Research and Practice: Suggestions for researchers are as follows: it is possible to say that the following themes can be further studied: the decision-making styles and self-esteem in decision-making concepts in different age groups and education levels; and identifying different variables related to these concepts and increasing the number of studies conducted with experimental arrangements involving different decision-making situations. For practitioners, seminars can be organized on this issue within the youth counseling centers working on the university campuses, organizing psycho-education programs for the development of young people's decision-making skills and emphasizing the importance of cognition in decision-making in these programs, as well as emphasizing emotions and uncertainty.