In this study, it was aimed to investigate the relationship between COVID-19 fear and intolerance of uncertainty and generalized anxiety disorder in individuals aged 18-65 years and older. Also, it was examined whether COVID-19 and intolerance of uncertainty predicted generalized anxiety disorder significantly. In this study, data were collected, using convenience sampling model, from a total of 843 people, including 547 females (64.9%) and 296 males (35.1%) in July and August 2020. The data collecting tools of the study were the COVID-19 Fear Scale, the Intolerance of Uncertainty Scale (IUS), and the General Anxiety Disorder Test (GAD-7). The correlations between COVID-19 fear total score and IUS total score, and sub-scales' scores, and GAD-7 total score were examined using the Pearson Product-Moment Correlation Coefficient technique. As a result of the analysis, it was seen that there were significant and positive relationships between COVID-19 fear total score and IUS total, as well as between subscales' scores and GAD-7. Additionally, the prediction level of COVID-19 fear and intolerance of uncertainty on generalized anxiety disorder was tested via Multiple Regression Analysis, and it was observed that the fear of COVID-19 and IUS total score, IUS1, IUS4 were significant predictors of generalized anxiety disorder.