Purpose We aimed to develop and validate the Musicians' Hearing Handicap Index (MHHI), a new self-evaluation tool for quantifying occupation-related auditory difficulties in music professionals. Although pure-tone audiometry is often considered the "gold standard" and is usually employed as the main instrument for hearing assessment, it cannot fully describe the impact of hearing dysfunction. The MHHI is an attempt to complement the hearing impairment assessment toolbox and is based on a unique approach to quantify the effects of hearing-related symptoms or hearing loss on the performance of musicians and other music industry professionals. Method An initial set of 143 questionnaire items was successively refined through a series of critical appraisals, modifications, and suggestions. This yielded an intermediate questionnaire consisting of 43 items, which was administered to 204 musicians and sound engineers. After exploratory factor analysis, the final form of the MHHI questionnaire was obtained, consisting of 29 items. The questionnaire's test-retest reliability, internal consistency, discriminating power, content validity, criterion validity, and aspects of construct validity and inherent conceptual structure were assessed. Results Exploratory factor analysis revealed a combination of four common factors for the 29 validated questionnaire items. They were named "impact on social and working lives," "difficulties in performance and sound perception," "communication difficulties," and "emotional distress." The MHHI was shown to be a valid and reliable instrument to assess musicians' and sound engineers' occupational difficulties due to hearing impairment and related symptoms. Conclusion The ability of the MHHI to discriminate between groups of music professionals with different auditory symptoms or pure-tone audiometry thresholds suggests that auditory symptoms might influence a professional's performance to an extent that cannot be assessed by a pure-tone audiogram.