The 16-item Athlete Mindfulness Questionnaire (AMQ) provides a comprehensive sport-specific measure of mindfulness for athletes. The AMQ is a dispositional measure that consists of three dimensions: present-moment attention, awareness, and acceptance. The AMQ was developed in a systematic approach with five related studies across four separated samples. Originally, acceptance items were phrased using negatively worded items but failed to provide convergent and concurrent validities. This might be due to inattention and confusion of athletes when trying to interpret the meaning of items. The AMQ with positively worded items of acceptance provided excellent model fit, acceptable internal consistencies, and well-established convergent and concurrent validities. Overall, the 16-item AMQ is a reliable and valid self-report measure of mindfulness in sports contexts. The AMQ can be used in future studies applying mindfulness training on promoting athletic performance and mental health.