Aim: This study reports the development and validation of a new self-report measure (MPRAQ) that assesses practical barriers to medication adherence. Methods: MPRAQ comprises fifteen statements describing practical barriers. Responses are scored on a 5-point Likert scale; higher scores indicate more practical barriers. Initial face validity was evaluated by cognitive testing with patients from a diabetes support group. Following refinement, internal reliability and construct validity were assessed in two samples: patients recruited via Amazon mTurk and the Nivel Dutch Healthcare Consumer Panel (COPA). Respondents completed the Beliefs about Medicines Questionnaire (BMQ - general and specific), and Medication Adherence Report Scale (MARS-5). The mTurk sample also completed the Perceived Sensitivity to Medicines questionnaire (PSM), and repeated MPRAQ two weeks later to assess test-retest reliability. Results: Face validity was evaluated in 15 patients (46% female; mean (SD) age 64(12) years). A total of 184 mTurk participants completed the questionnaire (in English) and 334 in COPA (in Dutch). Internal reliability was acceptable (mTurk α=0.89; COPA α=0.94). Construct validity was confirmed, with significant correlation between MPRAQ and BMQ-Specific Concerns (mTurk r=0.546, p<0.0001; COPA r=0.370, p<0.0001); BMQ-General Harm (mTurk r=0.504, p<0.0001; COPA r=0.219, p<0.0001); BMQ-General Overuse (mTurk, r=0.324, p<0.0001; COPA r=0.109, p=0.047), and PSM (mTurk only, r=0.463, p<0.0001), and a negative correlation with MARS-5 (mTurk r=-0.450, p<0.0001; COPA r=-0.260, p<0.0001). MPRAQ did not correlate with BMQ-Specific Necessity or BMQ-General Benefit. Correlation between MPRAQ baseline and 2-week follow-up scores confirmed test-retest reliability (r=0.745, p<0.0001; n=52). Conclusion: MPRAQ is a reliable and valid self-report measure of practical adherence barriers. Keywords: Adherence; MPRAQ; barriers; measure; medication; practicalities; questionnaire; validation. This article is protected by copyright. All rights reserved.