This work is an in-depth case study of an action science teaching/learning project, and the focus is on one practitioner's experience in learning the diagnostic skills of action science. Using the theory-of-action approach developed by Argyris and Schon, the study examines a series of episodes, critical incidents, and issues that arose during a reflective practicum in which the learner participated over a year and one half period. The study is unique in that not only is the learning experience examined from the learner's perspective, but the practitioner under study is the researcher herself. In applying the particular approach and methodology to studying in-depth part of the complex process of learning to become an action scientist, the goal is to contribute to the current, rather limited bank of knowledge in this area, and build understanding about what kinds of learning environments and processes might better facilitate the learning of future action scientist trainees.