The aim of the present research was to examine the efficacy of mindfulness based stress reduction on the mindfulness and assertiveness of students with test anxiety. The sample consisted of 45 subjects with test anxiety randomly selected from third grade guidance school girls and boys of Nowshahr city. The subjects were assigned randomly to experimental and control groups. The experimental group received training in minfulness based stress reduction. The instruments employed in this research were test anxiety inventory, mindfulness inventory and assertiveness scale. Multivariate analysis of variance showed significant differences between the group receiving training in mindfulness and the control group on the variables of mindfulness, assertiveness and test anxiety. Mindfulness based stress reduction affected the mindfulness, assertiveness and test anxiety of the students.