This study sought to examine the causes of team-based structure adoption among listed companies in Korea, with research hypotheses established based on rationality theories (rational choice theory, resource dependence theory, and organizational ecology theory) and legitimacy theories (institutional theory and network theory). Listed companies in Korea were the subjects of the study, and data were collected through telephone surveys and literature. The response rate for the telephone survey was 51.5 percent (400 out of a total of 773 companies responded), and research hypotheses related to the adoption of large-department-type team structures during the period from 1985 to 1998 were tested. The analytical model employed was the Weibull model from event history analysis. The analysis results showed that the legitimacy hypothesis had relatively greater explanatory power than the rationality hypothesis as a cause of team adoption. That is, coercive, mimetic, and normative isomorphism phenomena were strongly manifested in Korean firms' adoption of team-based structures. The results of additional analyses showed that, first, when organizational age is low, legitimacy acquisition is a relatively important factor; second, it was partially demonstrated that large firms adopt team-based structures to acquire rationality while small firms adopt them to acquire legitimacy; and third, it was revealed that the factors influencing team-based structure adoption differ by industry (manufacturing vs. non-manufacturing).