AbstractBackground and aimsDespite the last decade's significant development in the scientific study of work addiction/workaholism, this area of research is still facing a fundamental challenge, namely the need for a valid and reliable measurement tool that shows cross-cultural invariance and, as such, allows for worldwide studies on this phenomenon.MethodsAn initial 16-item questionnaire, developed within an addiction framework, was administered alongside job stress, job satisfaction, and self-esteem measures in a total sample of 31,352 employees from six continents and 85 cultures (63.5% females, mean age of 39.24 years).ResultsBased on theoretical premises and psychometric testing, the International Work Addiction Scale (IWAS) was developed as a short measure representing essential features of work addiction. The seven-item version (IWAS-7), covering all seven components of work addiction, showed partial scalar invariance across 81 cultures, while the five-item version (IWAS-5) showed it across all 85 cultures. Higher levels of work addiction on both versions were associated with higher job stress, lower job satisfaction, and lower self-esteem across cultures. The optimal cut-offs for the IWAS-7 (24 points) and IWAS-5 (18 points) were established with an overall accuracy of 96% for both versions.Discussion and conclusionsThe IWAS is a valid, reliable, and short screening scale that can be used in different cultures and languages, providing comparative and generalizable results. The scale can be used globally in clinical and organizational settings, with the IWAS-5 being recommended for most practical and clinical situations. This is the first study to provide data supporting the hypothesis that work addiction is a universal phenomenon worldwide.