A major fire incident in a Swedish underground mine made the personnel from the mining company and the rescue service realize their limited preparedness. It was the beginning of a collaboration project that included the development of a new exercise model for a more effective joint rescue operation practice. The aim of this study was to explore the collaborative learning process of exercise organizers from the rescue service, mining companies, the emergency medical service, a training company, and academia. The analysis was performed through the application of the theory cycle of expansive learning to the material consisting of documents from 16 collaboration meetings and 11 full-scale exercises. The learning process started by the participants questioning the present practice of the rescue operation and analyzing it by creating a flow chart. An essential part of the process was to model new tools in order to increase the potential for collaboration. The tools were examined and tested during collaboration meetings and implemented during full-scale exercises. The exercise organizers reflected that the process led to organizational development and a better understanding of the other organizations’ perspectives. Consequently, a tentative model for developing the learning process of exercise organizers was developed. © 2020 by the authors.