The purpose of this study was to increase what is known about how professionals engage in professional identity shift as they adapt to changing roles and expectations in the workplace. Given the organizational, institutional, and regulatory changes increasing the need for finance professionals to engage in business partnering, this study explored how finance/accounting professionals in the financial services industry transition to the role of business partner. The primary units of analysis were the 33 cases of role identity shift that emerged across the 15 subject interviews. The researcher assumed that the learning required to transition to business partner goes beyond skill acquisition, involving a "shift in professional identity." The conceptual framework was based on a model by Chreim et al. (2007), which emphasizes the impact of institutional and organizational factors alongside individual factors on professional identity construction. Ibarra and Petriglieri's (2010) conception of "identity play" was also used to examine how participants reinvented themselves as part of identity transition. The study's conclusions reinforced the interaction, as posited, between individual traits and characteristics and organizational/institutional factors. In early and mid-career cases, the role of the manager was found to enable professional identity shift, and identity play was found to be useful, but not essential, to professional identity transition. In late career cases, perspective taking (Van Rossum, 2013) was found to be used to navigate dis-equilibrating experiences and role conflict as part of the professional identity transition process. Additionally, female participants were found to place more emphasis on the relational aspects of business partnering as compared to males. Core recommendations for future research include further exploration into (1) the role of perspective taking in navigating identity shifts that involve high role conflict, (2) gender differences in how professionals conceptualize and approach business partnering, and (3) the impact of organizational and institutional culture on professional identity transition. Core recommendations for practice include emphasis on development of people managers given their pivotal role in enabling professional identity shift, and re-examination of career paths and change/learning programs designed to prepare professionals for business partnering. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]