Background:Programs for improving health status of patients with illness related to pain, such as headache, are often still in their infancy. Mindfulness-based stress reduction (MBSR) is a new psychotherapy that appears to be effective in treating chronic pain and stress. This study evaluated efficacy of MBSR in treatment of perceived stress and mental health of client who has tension headache. Materials and Methods: This study is a randomized clinical trial. Sixty patients with tension type headache according to the International Headache Classification Subcommittee were randomly assigned to the Treatment As Usual (TAU) group or experimental group (MBSR). The MBSR group received eight weekly classmates with 12-min sessions. The sessions were based on MBSR protocol. The Brief Symptom Inventory (BSI) and Perceived Stress Scale (PSS) were administered in the pre- and posttreatment period and at 3 months follow-up for both the groups. Results: The mean of total score of the BSI (global severity index; GSI) in MBSR group was 1.63 ± 0.56 before the intervention that was significantly reduced to 0.73 ± 0.46 and 0.93 ± 0.34 after the intervention and at the follow-up sessions, respectively (P < 0.001). In addition, the MBSR group showed lower scores in perceived stress in comparison with the control group at posttest evaluation. The mean of perceived stress before the intervention was 16.96 ± 2.53 and was changed to 12.7 ± 2.69 and 13.5 ± 2.33 after the intervention and at the follow-up sessions, respectively (P < 0.001). On the other hand, the mean of GSI in the TAU group was 1.77 ± 0.50 at pretest that was significantly reduced to 1.59 ± 0.52 and 1.78 ± 0.47 at posttest and follow-up, respectively (P < 0.001). Also, the mean of perceived stress in the TAU group at pretest was 15.9 ± 2.86 and that was changed to 16.13 ± 2.44 and 15.76 ± 2.22 at posttest and follow-up, respectively (P < 0.001). Conclusion: MBSR could reduce stress and improve general mental health in patients with tension headache.