Introduction: The purpose of the present ecological implementation field study is to evaluate the new classification of chronic pain as implemented in the 11th revision of the International Classification of Diseases ( ICD-11 ) with regard to clinical utility and interrater reliability. To evaluate the classification in a variety of settings, the study will be implemented in different low-, middle-, and high-income countries. Methods: The study will be conducted in 2 phases. Participating pain clinics of the first phase are located in India, Cuba, and New Zealand. Two or more clinicians per study center will use the ICD-11 classification of chronic pain to diagnose 75 to 100 consecutive new chronic pain patients per center. A structured classification algorithm will guide the diagnostic process. Interrater reliability will be analyzed for the first 20 consecutive new patients per center. Before the coding, a training workshop will introduce the clinicians to the new classification. The main outcome parameter of the ecological implementation field study is clinical utility. More specifically, this entails clinical utility ratings, interrater reliability, as well as the exhaustiveness of the classification and the mutual exclusiveness of the new chronic pain categories. Differences between countries with different cultural backgrounds and income levels will be analyzed. Perspective: The ecological implementation field study presented here will be implemented in several countries with different income levels. This increases the generalizability of the results and allows initial insight into the global applicability of the new chronic pain classification. A positive evaluation can facilitate the implementation of the classification.