Objective.— Examine whether acceptance and commitment additive therapy is effective in reducing the experience of sensory pain, disability, and affective distress because of chronic headache in a sample of outpatient Iranian females. Background.— Chronic headaches have a striking impact on sufferers in terms of pain, disability, and affective distress. Although several Acceptance and Commitment Therapy outcome studies for chronic pain have been conducted, their findings cannot be completely generalized to chronic headaches because headache‐related treatment outcome studies have a different emphasis in both provision and outcomes. Moreover, the possible role of Iranian social and cultural contexts and of gender‐consistent issues involved in Acceptance and Commitment Therapy outcomes deserve consideration. Methods.— This study used a randomized pretest–post‐test control group design. The sample was selected from consecutive female outpatients with chronic headache, attending and/or referred to a headache clinic in a governmental hospital from April 2011 to June 2011. In total, 80 female outpatients were interviewed, and after implementing inclusion/exclusion criteria, thirty females were considered eligible to participate in the study. Half (n = 15) were randomly selected to participate in the treatment group. Four participants of this group failed to complete the treatment sessions (n = 11). The Acceptance and Commitment Therapy group received the medical treatment as usual and 8 sessions of Acceptance and Commitment Therapy. The other half (n = 15) served as the control group that received only medical treatment as usual. The short form of McGill pain questionnaire, the migraine disability assessment scale, and the trait subscale of the state‐trait anxiety inventory were administered, which operationalized 3 dimensions of impact of chronic headache, sensory pain, disability, and emotional distress, respectively, to explore the impact of recurrent headache episodes. Pretest and post‐test measures on these 3 dimensions of impact were the primary outcome measures of this study. Analyses of covariance with the pretreatment score used as a covariate were conducted on pain intensity, degree of disability, and level of affective distress before and after therapy to assess therapeutic intervention effectiveness. Results.— Chronic tension type of headache (63%) and chronic migraine without aura (37%) were the headache types reported by the participants. Data analyses indicated the significant reduction in disability (F[1,29] = 33.72, P < .0001) and affective distress (F[1,29] = 28.27, P < .0001), but not in reported sensory aspect of pain (F[1,29] = .81, P = .574), in the treatment group in comparison with the control group. Conclusions.— The effectiveness of a brief acceptance and commitment additive therapy in the treatment of Iranian outpatient females with chronic headache represents a significant scientific finding and clinical progress, as it implies that this kind of treatment can be effectively delivered in a hosp...