The emphasis on professionalism in public administration has highlighted the importance of city managers and their role in managing cities effectively. While there are various avenues for city managers to improve their professionalism, such as a Master of Public Administration (MPA) degree, there has been limited research on other organizations that facilitate professionalism. This paper focuses on the International City/County Management Association (ICMA) credentialing program. ICMA is a nationally recognized organization that helps dictate professional norms among city managers. The purpose of this paper is to explore the motivations of city managers who pursue additional credentials and to identify the types of city managers who are more likely to attain professional certification. I argue that the ambition of city managers, as measured through their career path, is related to their pursuit of professionalism. Specifically, city managers with a diagonal career path are more likely to attain additional professional certification compared to those with a ladder career path because it signals their promising ability to future employers, namely city councils. To test this hypothesis, this paper uses two datasets. The first dataset examines the career paths of city managers in California, Florida, and North Carolina from 2012 to 2023. The second dataset focuses on newly hired chief administrators from 2021 to 2023 across the United States, drawing data from the ICMA job advertising information. From these two datasets, I find that city managers with diagonal career paths are more likely to possess ICMA credentials than those with ladder career paths.