Background: In 1990, the United States’ Institute of Medicine promoted the principles of outcomes monitoring in the alcohol and other drugs treatment field to improve the evidence synthesis and quality of research. While various national outcome measures have been developed and employed, no global consensus on standard measurement has been agreed for addiction. It is thus timely to build an international consensus. Convened by the International Consortium for Health Outcomes Measurement (ICHOM), an international, multi-disciplinary working group reviewed the existing literature and reached consensus for a globally applicable minimum set of outcome measures for people who seek treatment for addiction. Methods: To this end, 26 addiction experts from 11 countries and 5 continents, including people with lived experience (n = 5; 19%), convened over 16 months (December 2018–March 2020) to develop recommendations for a minimum set of outcome measures. A structured, consensus-building, modified Delphi process was employed. Evidence-based proposals for the minimum set of measures were generated and discussed across eight videoconferences and in a subsequent structured online consultation. The resulting set was reviewed by 123 professionals and 34 people with lived experience internationally. Results: The final consensus-based recommendation includes alcohol, substance, and tobacco use disorders, as well as gambling and gaming disorders in people aged 12 years and older. Recommended outcome domains are frequency and quantity of addictive disorders, symptom burden, health-related quality of life, global functioning, psychosocial functioning, and overall physical and mental health and wellbeing. Standard case-mix (moderator) variables and measurement time points are also recommended. Conclusions: Use of consistent and meaningful outcome measurement facilitates carer–patient relations, shared decision-making, service improvement, benchmarking, and evidence synthesis for the evaluation of addiction treatment services and the dissemination of best practices. The consensus set of recommended outcomes is freely available for adoption in healthcare settings globally.