From an organizational cognition standpoint, we approach organizational design as an ongoing creative sensemaking process. This study examined the role of expertise in the cognitive problem-solving patterns underlying design processes and the resulting organizational forms. The simulated problem elicited the mental models applied by naives, novices, and experts in designing an organization. The thinking-aloud protocol analysis revealed quantitative and qualitative expert/nonexpert differences in problem-solving strategies, the time spent on problem representation, and the justifications and difficulties expressed in the course of the design process. In addition, our results showed that naives created organizations consistent with mechanistic structures, while novices and experts created organizations consistent with organic structures. We discuss the implications of these findings for the understanding of the cognitive basis of organizational design and the development of effective training programs.