<p>With manufacturing companies facing societal and economic challenges, their error risk in manual assembly lines is increasing. A demographic change can be observed in many industrialized countries, negatively influencing performance levels. Furthermore, a shortage of skilled workers with the required qualifications is another challenge for companies. The increasing product variance and the pressure regarding costs, quality, and time imply a higher load on the employees. This discrepancy between rising load and potentially diminishing performance levels can lead to increasing errors in manual assembly. Developing a taxonomy of error-influencing factors for manual assembly lines is a crucial step, as it enables a systematic decision on preventive measures to hinder the development of errors. This contribution introduces this taxonomy, which is the core of the research and is based on a structured literature review, numerous expert interviews, and an expert workshop. Furthermore, a method for selecting the most relevant error-influencing factors for companies’ individual use cases is presented, offering a practical solution to a pressing industry problem.</p>