Substance Use Disorders (SUDs) are a national public health crisis. However, there is minimal existing research literature on the role of the nurse working in SUD treatment. The purpose of this study was to describe the meaning of the professional role of the registered nurse working in the SUD setting. The study utilized a Heideggerian Phenomenological approach with a modified Colaizzi method for analysis and interpretation. The nine study participants, two males and seven females, aged 27-60 had worked in SUD treatment for 1-37 years. Three major themes, with sub-themes, emerged: Defining the Role for Self; Learning the Role; and Navigating with Ease in an Unchangeable Culture. Findings demonstrated that nurses in SUD treatment value their role and the care of patients with SUDs. Patient recovery or relapse influenced job satisfaction. Significantly, the findings highlighted an outdated role with rigid boundaries and no real contemporary identity. Findings can be used to address the need for a contemporary SUD nursing identity and to support ongoing involvement of nurses in health policy related to SUDs.