BackgroundImproving sports performance and reducing anxiety is one of the most important goals of athletes. Recurrence of symptoms and treatment cessation are common problems with common interventions. Approaches based on mindfulness-acceptance-commitment (MAC) can be a response to these limitationsObjectiveThe main purpose of the present study was to determine effectiveness of the mindfulness-acceptance-commitment-based approach to athletic performance enhancement and sports competition anxiety in students who have had athletic experience for 3 to 5 years.MethodsThis randomized clinical trial was conducted at the Faculty of Educational Sciences of Iran University of Medical Sciences in Tehran, Iran, from May 1, 2017 to September 15, 2017. A total of 31 students were randomly assigned to experimental (n=15) and control groups (n=16). The experimental group received the protocol Mindfulness-Acceptance-Commitment (MAC) for 8 sessions. Subjects completed the Charbonneau Sports Performance Questionnaire, Action and Acceptance Questionnaire (AAQ) and Sports Competition Anxiety Test (SCAT) Questionnaire. Data analysis was conducted by using multivariate covariance analysis (MANCOVA) by SPSS-22.ResultsThe results of the study indicated that the MAC approach increases significantly the performance of basketball playing athletes (p<0.05). Furthermore, the MAC approach decreases significantly experiential avoidance and sports anxiety in athletes (p<0.05). The size of the difference between the groups is moderate (Eta squared).ConclusionsThis study revealed that the mindfulness-acceptance-commitment-based approach is an effective intervention to increasing athletic performance and reducing experiential avoidance and sports anxiety in athletes.Trial registrationThe trial was registered at the Iranian Registry of Clinical Trials (http://www.irct.ir) with the Irct ID: IRCT20170409033333N1.FundingThis study has been financially supported by the Research Deputy of Iran University of Medical Sciences (Code: 95-04-185-29333).