Background <p>Appearance beliefs may negatively impact body image and psychological wellbeing. Accordingly, this study aimed to develop the Metacognitions about Physical Appearance Questionnaire (MPAQ).</p> Method <p>An initial 30-items were formulated after thematic analysis of clinicians’ (<i>N</i> = 23) reports regarding appearance-based metacognitive beliefs and feedback from laypeople. A cross-sectional design across two non-clinical samples (Sample 1 <i>N</i> = 370, <i>M</i>_age = 39.36, 79% female; Sample 2 <i>N</i> = 463, <i>M</i>_age = 30.88, 81% female) was then used to determine the factor structure, reliability, and validity of the MPAQ.</p> Results <p>Initial factor analyses supported a reduced 20-item MPAQ across two subscales (positive and negative beliefs about worry or rumination on physical appearance). Correlated residuals and cross-loadings detected with confirmatory factor analysis further reduced the MPAQ to 15 items (seven for positive, eight for negative). Reliability and convergent, discriminant, and incremental validity of the MPAQ-15 were supported in both samples.</p> Conclusion <p>The current study provides preliminary support for the MPAQ as a reliable and valid measure of metacognitions about physical appearance. The measure may be beneficial for researchers and clinicians working with individuals with body image concerns. Further psychometric evaluation of the MPAQ is recommended, including test-retest reliability and validation of the measure in diverse populations.</p>