The Generalized Anxiety Disorder (GAD) is one of the most chronic and detrimental disorders and it is considered a common disorder in childhood and adolescence. Furthermore, this disorder is associated with many problems in the health domain. As such, this study attempted to gauge the impact of mindfulness-based stress reduction on intolerance of uncertainty and anxiety sensitivity among students with generalized anxiety disorder. Therefore, it was attempted to run a quasi-experimental research, including a pre-test, a post-test and a control group, among high schools of Robat Karim in Tehran province. Having used the purposive sampling method, 30 students diagnosed with generalized anxiety disorder, intolerance of uncertainty and high anxiety sensitivity were selected. Then, they were randomly assigned to experimental (15 students) and control groups (15 students). Consequently, the mindfulness program was introduced to the experimental group in 8 sessions and the control group received no treatment. It should be noted that groups were assessed before and after treatment with generalized anxiety scale, anxiety sensitivity and intolerance of uncertainty. The results of analysis of covariance showed that mindfulness-based stress reduction programs significantly reduced the symptoms of generalized anxiety disorder, anxiety sensitivity and intolerance of uncertainty. Since mindfulness reduces the levels of two key components of generalized anxiety disorder, namely intolerance of uncertainty and anxiety sensitivity, it seems appropriate to make use of this program in the treatment of generalized anxiety disorder.