Abstract: This study investigates the knowledge capacity and the competitive relationship between cities in contemporary globalization. Drawing upon the global city thesis regarding advanced producer services and the city network model, this study measures the concentration and mobility of knowledge workers between three Australian global cities: Sydney, Melbourne, and Brisbane. It argues that knowledge workers are important agents in the making of urban knowledge space and intercity knowledge flow. It finds that Sydney's dominance in the Australian urban system has been strengthened despite challenges from Melbourne and Brisbane in certain knowledge sectors. The findings ascertain the linkage between the ranking of a global city and its knowledge capacity. They provide new insights into the current debates on Australian global cities and suggest possible new directions for global city aspirations, in the cases of Melbourne and Brisbane, in particular. Conceptually and methodologically, this study is an effort to bridge the global-city and the knowledge-city discourses, whose cross-fertilization suggests a potential need for new policy thinking.